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Guides, tutorials, and best practices for qPCR data analysis.
How to Analyze qPCR Data: A Complete Guide
A step-by-step qPCR analysis workflow: QC raw Ct values, pick a quantification method, normalize, compute fold change, run stats — done right.
March 13, 2026 ★ FeaturedWhat Happened to qbase+ — and Why I Built VoilaPCR
I went looking for qbase+ and it was gone. So I built a browser-based qPCR analysis tool that does what qbase+ did, without the pain.
October 4, 2026CFX Maestro to Publication Figure in 60 Seconds
The fastest route from a Bio-Rad CFX96 run to a ΔΔCt bar chart with error bars and p-values: one export from CFX Maestro, one upload, no Excel.
October 4, 2026How to Open a QuantStudio .eds File Without the Software
A QuantStudio .eds run file is a zip of XML and text, not a locked binary. Here is what is inside, how to read the Ct table, and the one tool that analyzes it directly.
October 4, 2026QuantStudio Design & Analysis 2: From Export to Fold Change
How to export results from QuantStudio Design & Analysis 2 (Sample, Target, Cq columns) and get ΔΔCt fold changes without rebuilding the spreadsheet.
September 24, 2026How to Export RDML Files from Bio-Rad CFX Maestro Software
Step-by-step guide to exporting RDML files from CFX Maestro for use in third-party qPCR analysis tools. Covers both CFX Maestro 1.1 and 2.0+.
September 23, 2026How to Set the Ct Threshold Correctly in SYBR Green qPCR
Where to place the Ct threshold in SYBR Green qPCR, why auto-threshold often gets it wrong, and how to set it manually for reliable data.
September 22, 2026Replicate Ct Standard Deviation Above 0.5: When to Exclude and When to Troubleshoot
High Ct standard deviation between qPCR replicates — when to drop the outlier, when to rerun, and how to find the actual cause. Practical thresholds and decision logic.
September 21, 2026QuantStudio vs CFX96: Which qPCR Instrument Should You Actually Buy for a New Lab?
A practical comparison of the QuantStudio and CFX96 for new labs — covering optics, software, throughput, cost, and the things sales reps won't mention.
September 18, 2026Amplification in No Template Control Wells: 5 Hidden Causes
Late Ct in your NTC wells doesn't always mean contamination. Here are five real causes of NTC amplification and how to fix each one.
September 17, 2026How to Calculate qPCR Primer Efficiency from Standard Curve Slope
Calculate primer efficiency from your standard curve slope using E = 10^(-1/slope) - 1. Worked examples, troubleshooting, and what to do when efficiency falls outside 90-110%.
September 16, 2026Ct Values Increasing Between Replicate Runs: What Went Wrong
Ct values creeping up between repeat qPCR runs? Here's how to diagnose whether it's degradation, reagent issues, or instrument drift — and how to fix it.
September 15, 2026Why Does My Standard Curve R² Drop Below 0.98 — and How to Fix It
A low R² on your qPCR standard curve usually traces back to pipetting, template quality, or curve design. Here's how to diagnose and fix it.
September 14, 2026When Your Negative Control Has a Lower Ct Than Your Treated Samples
Your untreated control shows a lower Ct than your treated group. Here's how to tell if that's real biology or a technical problem — and what to do next.
September 11, 2026How Much cDNA Template to Use in qPCR Reactions
Practical guide to cDNA input amounts for qPCR — how much to use, when to dilute, and how to avoid inhibition and pipetting errors.
September 10, 2026CFX96 Baseline Subtraction: Auto vs Manual Settings — When to Override the Software
Auto baseline on the CFX96 usually works. Here's how to tell when it doesn't, and exactly how to set manual baseline cycles for cleaner Ct values.
September 9, 2026Welch's t-Test vs Student's t-Test for qPCR Fold Change Significance
When testing qPCR fold change significance, Welch's t-test is almost always the better choice. Here's why, with worked examples on ΔCt data.
September 8, 2026What R² Value Is Acceptable for qPCR Standard Curves
Your qPCR standard curve R² should be ≥0.98. Here's what that number actually tells you, when it misleads, and what to check when it drops.
September 7, 2026One Sample Has Much Higher Ct Than Others: Troubleshooting
When one qPCR sample gives a Ct 5-10 cycles higher than the rest, here's how to figure out if it's real biology or a technical artifact.
September 4, 2026GraphPad Prism qPCR Analysis: How to Run ΔΔCt Calculations Step-by-Step
A practical walkthrough of setting up ΔΔCt analysis in GraphPad Prism, from organizing your Ct data to running stats on fold changes correctly.
September 3, 2026Melt Curve Shows Two Peaks: Primer Dimer or Multiple Products?
Two peaks on your melt curve? Here's how to tell if it's primer dimers or off-target amplification — and what to do about each.
September 2, 2026Can I Compare qPCR Results Across Different Runs?
When it's safe to compare qPCR data across plates and when it isn't — with practical strategies to make inter-run comparisons reliable.
September 1, 2026How to Export Raw Fluorescence Data from QuantStudio Real-Time PCR Systems
Step-by-step guide to exporting raw fluorescence data from QuantStudio 3, 5, 6, and 7 systems, including file formats and common pitfalls.
August 31, 2026NTC Wells Showing Amplification After Cycle 30: When to Worry and When to Move On
Late amplification in no-template controls is common but not always a problem. Here's how to interpret NTC Ct values and when they actually threaten your data.
August 28, 2026How to Analyze qPCR Data When Your Housekeeping Genes Aren't Stable
What to do when GAPDH, ACTB, or other reference genes shift across your conditions. Practical strategies for valid normalization when housekeeping genes vary.
August 27, 2026Ct Values Above 35: Should You Trust Them?
Late Ct values are common but rarely reliable. Here's how to decide whether a Ct of 36 is real signal or noise, with practical cutoffs and controls.
August 26, 2026Standard Curve Slope Outside -3.1 to -3.6: What to Do
Your qPCR standard curve slope is outside the acceptable range. Here's what it actually means, how to diagnose the cause, and how to fix it.
August 25, 2026Converting RDML Files to Excel for Custom Analysis
How to extract Ct values, amplification curves, and metadata from RDML files into Excel for flexible downstream qPCR analysis.
August 24, 2026Amplification Curve Plateau Phase Too Low: Causes and Solutions
Low plateau fluorescence in qPCR usually points to reagent limitation, suboptimal primer design, or dye/probe issues. Here's how to diagnose and fix it.
August 21, 2026Biological vs Technical Replicates in qPCR: When You Need Which
Biological replicates measure real variation between samples. Technical replicates catch pipetting errors. Here's how to decide what your qPCR experiment actually needs.
August 20, 2026Why Do My Technical Replicates Have Different Ct Values?
Technical replicate Ct values rarely match perfectly. Here's how much variation is normal, what causes it, and when you should actually worry.
August 19, 2026Primer Efficiency Below 90% — What It Means and How to Fix It
Low qPCR primer efficiency skews your fold-change calculations. Here's what causes it and how to systematically fix it.
August 18, 2026How to Set the Ct Threshold in qPCR Analysis
Where to place the Ct threshold in qPCR — and why the default auto-threshold on your instrument isn't always right. A practical guide with real examples.
August 17, 2026Inter-Run Calibrator Ct Values Shifted By 0.8 Cycles — What It Means and What to Do
Your IRC Ct shifted by 0.8 cycles between runs. Here's how to diagnose whether it's a reagent issue, instrument drift, or something you can safely correct.
August 14, 2026Can I Analyze qPCR Data Without a Standard Curve?
Yes — most relative quantification doesn't need a standard curve. Here's when you can skip it, when you can't, and how to do it right.
August 13, 2026Why Your LightCycler 96 Reports Melting Temperatures 2°C Lower Than Expected
LightCycler 96 Tm values often read ~2°C below other instruments. Here's why it happens and when it actually matters for your data.
August 12, 2026Why Your Amplification Curves Plateau at Different Fluorescence Heights
Different plateau heights in qPCR amplification curves are normal — here's what causes them, when they matter, and when you can safely ignore them.
August 11, 2026ROX Passive Reference Dye: Which Instruments Actually Need It
ROX normalizes well-to-well fluorescence on some qPCR instruments but is unnecessary on others. Here's which machines need it and what concentration to use.
August 10, 2026How Much cDNA Template to Use Per qPCR Reaction Well
Practical guidance on cDNA input amounts for qPCR — how to pick the right dilution, avoid inhibition, and stay in the linear range.
August 7, 2026Single Well Outlier in qPCR Triplicates: Exclude It or Report With Error Bars?
When one of your qPCR triplicates is off, should you drop it or keep it? Practical criteria for excluding outlier wells without biasing your data.
August 5, 2026Exporting Mic qPCR Data to GraphPad Prism: What Actually Works
How to get data out of the Bio Molecular Systems Mic qPCR cycler and into GraphPad Prism without breaking your analysis. Practical export steps and formatting tips.
August 4, 2026Calculating Fold Change When Your Control Group Has a Higher Ct Than Your Treated Group
What it means when your control Ct is higher than your treated group, and how to correctly calculate fold change without flipping the math.
August 3, 2026No Amplification in Positive Control After Freeze-Thaw Cycles: What's Actually Degraded and How to Fix It
Positive control failing after freeze-thaw cycles? Here's how to diagnose whether it's your template, primers, or master mix — and prevent it next time.
July 31, 2026Why Do My Housekeeping Genes Vary By More Than 1 Ct?
Housekeeping genes shifting >1 Ct across samples? Here's why it happens, when it actually matters, and how to fix it before it wrecks your normalization.
July 30, 2026Standard Curve Slope Between -3.1 and -3.6: What the Math Actually Means and Which Equations to Use
Your qPCR standard curve slope falls between -3.1 and -3.6. Here's how to calculate efficiency, when to use Livak vs. Pfaffl, and what to do at the edges.
July 29, 2026How to Convert QuantStudio RDML Files to Excel for Analysis
Step-by-step methods to export QuantStudio RDML files to Excel, including free tools, Python scripts, and common pitfalls with Ct data extraction.
July 28, 2026One Sample Has Ct Values 3 Cycles Higher Than Others: What Happened
When one qPCR sample gives Ct values ~3 cycles higher across all targets, the problem is almost always input amount — not biology. Here's how to diagnose it.
July 27, 2026How to Set Ct Threshold Correctly in QuantStudio Software
A practical guide to setting the Ct threshold in QuantStudio software — when auto-threshold works, when it doesn't, and how to fix it manually.
July 24, 2026NTC Showing Amplification at Ct 32: Is My Experiment Ruined?
A Ct of 32 in your no-template control is a real problem. Here's how to tell if it invalidates your data and what's causing it.
July 23, 2026Technical Replicates vs Biological Replicates in qPCR: How Many Do You Actually Need?
Technical vs biological replicates in qPCR serve different purposes. Here's how many of each you need and why most labs over-invest in one and under-invest in the other.
July 22, 2026Primer Dimer in Some Wells But Not Others: How to Fix
Primer dimers appearing in random wells but not others? Here's why it happens and how to fix it without redesigning your primers.
July 21, 2026qPCR Efficiency Between 90-110%: What the Numbers Actually Mean
What qPCR efficiency really measures, why 90-110% is the accepted range, and what to do when your standard curve says otherwise.
July 20, 2026Why Are My Ct Values Above 35 — and Should I Be Worried?
Late Ct values don't always mean bad data. Here's how to decide whether a Ct above 35 is real signal, background noise, or a sign something went wrong.
July 17, 2026Your Housekeeping Gene Ct Value Changes Between Tissues — Now What?
When GAPDH or ACTB Ct values shift across tissue types, your normalization is compromised. Here's how to diagnose the problem and pick stable reference genes.
July 16, 2026Stop Running Statistics on Fold Change Values — Use ΔCt Instead
Fold changes from qPCR are ratios, not normally distributed. Run your t-tests and ANOVAs on ΔCt values, then convert to fold change for reporting.
July 15, 2026Two Peaks on Your qPCR Melt Curve: What They Mean and What to Do
A double peak on your SYBR Green melt curve usually means primer dimers or off-target amplification. Here's how to diagnose and fix it.
July 14, 2026How Much Template DNA or cDNA to Use Per qPCR Reaction
Practical guidelines for template input in qPCR — how much cDNA or gDNA to load, what happens when you use too much, and how to troubleshoot inhibition.
July 13, 2026No Amplification in Known Positive Samples — A Practical Troubleshooting Checklist
Your positive control isn't amplifying. Here's a systematic checklist to find the problem — from reagent failures to template issues — fast.
July 10, 2026Why Does My mRNA Target Have Ct 28 But Protein Is Undetectable?
A Ct of 28 suggests decent mRNA expression, but missing protein is common. Here's how to troubleshoot the mRNA-protein disconnect in your experiments.
July 9, 2026How to Analyze qPCR Data in GraphPad Prism With Error Bars
Step-by-step guide to plotting qPCR fold-change data in GraphPad Prism with correct error bars — calculated from ΔCt, not fold change.
July 8, 2026Comparing SYBR Green Results Across Two Different Instruments
How to compare qPCR data from two different instruments like QuantStudio and CFX96. Practical steps for aligning Ct values, baselines, and thresholds.
July 7, 2026Standard Curve Slope -3.1 to -3.6: What Efficiency Is Acceptable for qPCR?
What qPCR efficiency range is actually acceptable? How to interpret standard curve slopes between -3.1 and -3.6, and what to do when you fall outside.
July 6, 2026Calculating Fold Change When Your Control Has a Higher Ct Than Your Treatment
What it means when your treatment group has a lower Ct than your control — and how to correctly calculate and interpret fold change in that situation.
July 3, 2026RNA Integrity Number Below 7: Can I Still Trust My qPCR Results?
RIN below 7 doesn't automatically invalidate your qPCR data. Here's when degraded RNA matters, when it doesn't, and how to tell the difference.
July 2, 2026How to Set Ct Threshold in QuantStudio Design & Analysis Software
A practical guide to setting the Ct threshold manually in QuantStudio software — when auto-threshold fails, how to pick a value, and what actually matters.
July 1, 2026No Template Control Shows Ct 38: Do I Need to Rerun?
Your NTC came up at Ct 38. Is it contamination or background noise? Here's how to decide whether to rerun or trust your data.
June 30, 2026Your Primer Efficiency Is 90-110% But Results Still Look Wrong — Now What
Primer efficiency passes the textbook cutoff but your qPCR fold changes don't make sense. Here's where to look when the standard curve lies to you.
June 29, 2026How to Export RDML Files From Bio-Rad CFX Maestro
Step-by-step guide to exporting RDML files from CFX Maestro software for use in third-party qPCR analysis tools. Covers both CFX Maestro 1.1 and 2.0.
June 26, 2026My Positive Control Is Shifting Between Runs—Causes and Solutions
Positive control Ct values drifting between qPCR runs? Here's how to diagnose whether it's your template, your reagents, or your instrument.
June 25, 2026Should I Normalize to Multiple Reference Genes in qPCR?
When one reference gene isn't enough: how to normalize to multiple HKGs, when it actually matters, and how to do the math correctly.
June 24, 2026Converting qPCR Ct Values to Copy Number Without a Standard Curve
How to estimate absolute copy number from Ct values when you don't have a standard curve — methods, math, assumptions, and when it actually works.
June 23, 2026Ct Values Above 35: Reliable or Noise?
When should you trust a Ct of 36 or 37? Practical guidelines for interpreting late-cycle amplification in qPCR and when to call it background.
June 22, 2026Why Are My qPCR Triplicates So Variable (and How to Fix It)
High Ct spread across qPCR triplicates? Here's how to diagnose whether it's a pipetting problem, template issue, or something else — and how to fix it.
June 19, 2026Inter-Run Calibrator Replicates Varying by 0.3 Ct — Is That Acceptable?
How much Ct variation in your inter-run calibrators is too much? We break down acceptable ranges, what causes drift, and when to re-run.
June 18, 2026Mic qPCR Data Analysis: Export Options, File Formats, and How to Actually Work With Your Data
How to export data from the Bio Molecular Systems Mic qPCR cycler, what file formats you get, and how to handle compatibility issues in downstream analysis.
June 17, 2026My Fold Change Is 1.5—Is That Biologically Significant?
A 1.5-fold change by qPCR: real or noise? How to assess biological significance when your effect size is small but your p-value is fine.
June 16, 2026Manual vs. Auto Baseline Correction in qPCR: When to Override Your Software
Auto baseline works most of the time — until it doesn't. Learn when manual baseline correction matters and how to set it correctly.
June 15, 2026When to Use Welch's t-Test Instead of Student's for qPCR Data
Student's t-test assumes equal variance. Your qPCR data probably doesn't have it. Here's when and why Welch's t-test is the better default.
June 12, 2026GraphPad Prism vs Excel for qPCR Statistical Analysis: Which One Should You Actually Use?
A practical comparison of Prism and Excel for qPCR stats — what each does well, where each fails, and when you need neither.
June 11, 2026qPCR Amplification Plateau Lower Than Expected — What Happened
Low fluorescence plateau in qPCR? Here's what actually causes it — reagent depletion, inhibitors, suboptimal probe — and how to fix it.
June 10, 2026Do I Need a Standard Curve for Every qPCR Plate?
When you actually need a standard curve on every qPCR plate, when you can skip it, and how to validate the shortcut without compromising your data.
June 9, 2026Converting Rotor-Gene Data to RDML Format for Analysis
How to export Rotor-Gene Q data and convert it to RDML format for use in analysis tools, with practical steps and common pitfalls.
June 8, 2026How Many Cycles Should I Run for Gene Expression qPCR?
40 cycles is standard for gene expression qPCR, but the reasoning matters. Here's when 40 is right, when 45 helps, and when fewer is fine.
June 5, 2026Biological Replicates Showing Different Ct Value Patterns — Why It Happens and When to Worry
Biological replicate Ct values diverging? Here's how to tell if it's real biology, sample prep issues, or a problem worth troubleshooting.
June 4, 2026My qPCR Standard Curve R² Is 0.97—Is That Good Enough?
An R² of 0.97 on your qPCR standard curve looks decent but often signals a real problem. Here's how to diagnose it and when to worry.
June 3, 2026CFX96 vs QuantStudio 3: Which qPCR Machine Belongs in Your Core Lab?
A practical comparison of the Bio-Rad CFX96 and Thermo QuantStudio 3 for shared-use core labs—throughput, software, data export, and what actually matters day-to-day.
June 2, 2026Can You Use GAPDH and ACTB Together as Reference Genes?
When pairing GAPDH and ACTB as reference genes makes sense, when it doesn't, and how to evaluate their stability in your specific experiment.
June 1, 2026Standard Curve Slope of -3.1 vs -3.3: Does It Matter?
A qPCR standard curve slope of -3.1 vs -3.3 both fall in the acceptable range, but the difference changes your calculated concentrations. Here's by how much.
May 29, 2026NTC Wells Amplifying After Cycle 35—Problem or Normal?
Late Ct values in your no-template controls don't always mean contamination. Here's how to interpret NTC amplification after cycle 35 and when to actually worry.
May 28, 2026Exporting QuantStudio Data to Excel for Delta Delta Ct Analysis
How to export QuantStudio qPCR data to Excel and set up a proper ΔΔCt calculation — file formats, common pitfalls, and a faster alternative.
May 27, 2026How to Handle qPCR Technical Replicates with One Outlier
One of your three technical replicates looks off. Here's when to drop it, when to keep it, and how to make that call defensibly.
May 26, 2026Your qPCR Efficiency Is 90-110% But Results Still Look Wrong — Here's Why
Passing efficiency doesn't guarantee accurate qPCR results. Here's what else goes wrong and how to systematically find the real problem.
May 25, 2026Why Is My Reference Gene Ct Value Above 30 — And When to Worry
High Ct values for GAPDH, ACTB, or other reference genes usually point to a sample problem, not a primer problem. Here's how to diagnose and fix it.
May 22, 2026How to Set the Ct Threshold in qPCR (And Why It Matters)
Where you place the Ct threshold changes your data. Here's how to set it correctly — manually and automatically — and when the default is wrong.
May 21, 2026Primer Dimer vs Nonspecific Amplification: How to Tell the Difference
Melt curve has extra peaks? Here's how to distinguish primer dimers from nonspecific amplification — and what to do about each.
May 20, 2026One-Step vs Two-Step RT-qPCR: Choosing the Right Workflow
When should you use one-step vs two-step RT-qPCR? A practical comparison of sensitivity, throughput, flexibility, and when each workflow actually matters.
May 19, 2026Replicate Variability in qPCR: How Much Is Too Much?
How much Ct spread between qPCR replicates is acceptable? Practical thresholds, what causes variability, and when to drop an outlier.
May 18, 2026How to Calculate and Interpret qPCR Amplification Efficiency
A practical guide to calculating qPCR amplification efficiency from standard curves, what the numbers actually mean, and when efficiency matters most.
May 15, 2026What Is a Good Ct Value in qPCR? Ranges, Context, and When to Worry
Learn what Ct values actually mean in qPCR, what ranges to expect for common targets, and when a high or low Ct signals a real problem.
May 14, 2026CFX96 vs QuantStudio: Comparing qPCR Export Formats and What They Mean for Your Analysis
A practical comparison of export file formats from Bio-Rad CFX96 and Applied Biosystems QuantStudio, and how to handle each for downstream analysis.
May 13, 2026How to Validate Reference Genes with geNorm and NormFinder
Step-by-step guide to validating qPCR reference genes using geNorm and NormFinder — with real examples, interpretation tips, and common mistakes.
May 12, 2026How to Statistically Analyze qPCR Fold Change Data (Without Getting It Wrong)
Run statistics on ΔCt values, not fold changes. Here's exactly how to analyze qPCR data with t-tests, ANOVA, and proper error propagation.
May 11, 2026RT-qPCR vs qPCR: They're Not the Same Assay
RT-qPCR measures RNA via a reverse transcription step; qPCR amplifies DNA directly. Here's what actually differs and why the distinction matters.
May 8, 2026How to Export and Analyze QuantStudio qPCR Data
A practical guide to exporting qPCR data from QuantStudio software and analyzing it properly — file formats, Ct extraction, and common pitfalls.
May 7, 2026NTC Amplification in qPCR: What It Means and When to Worry
Late Ct in your no-template controls doesn't always mean contamination. Here's how to interpret NTC amplification and when it actually invalidates your data.
May 6, 2026How to Analyze qPCR Data with Biological Replicates
A practical guide to analyzing qPCR data with biological replicates — when to average, what to plot, and which statistical tests to run on ΔCt values.
May 5, 2026Absolute vs Relative Quantification in qPCR: Which One Do You Actually Need?
When to use absolute vs relative quantification in qPCR, how each method works, and the practical trade-offs most protocols gloss over.
May 4, 2026qPCR Standard Curve Best Practices and Common Mistakes
How to build a reliable qPCR standard curve: dilution series setup, efficiency calculations, and the mistakes that quietly wreck your absolute quantification.
May 1, 2026How to Normalize qPCR Data with Multiple Reference Genes
Using multiple reference genes in qPCR improves normalization accuracy. Here's how to combine them correctly using geNorm, NormFinder, or a simple geometric mean.
April 2, 2026Multiplex qPCR: A Practical Guide to Running Multiple Targets in One Well
How to design, optimize, and troubleshoot multiplex qPCR — primer/probe design, spectral crosstalk, efficiency matching, and common pitfalls.
March 23, 2026How to Design qPCR Primers That Actually Work
Practical primer design rules for qPCR: Tm matching, amplicon length, specificity checks, and the validation steps most protocols skip.
March 19, 2026The Pfaffl Method: When Your Primer Efficiencies Make ΔΔCt Unreliable
When qPCR primer efficiencies differ between target and reference genes, the Pfaffl method gives you accurate fold changes. Here's how to use it.
March 16, 2026Melt Curve Analysis in qPCR: What It Tells You and When to Worry
How to read melt curves in SYBR Green qPCR, spot primer dimers, identify off-target products, and decide when a run is trustworthy.
March 13, 2026SYBR Green vs TaqMan: When to Use Each Chemistry
A practical guide to choosing between SYBR Green and TaqMan for your qPCR experiments — based on cost, specificity, and what your project actually needs.
March 6, 2026Choosing the Best Reference Genes for qPCR
How to pick, validate, and use the right housekeeping genes for accurate normalization in RT-qPCR experiments.
March 6, 2026How to Calculate DDCt (Livak Method): A Complete Guide
Learn the delta-delta Ct method step by step, including the math, assumptions, common mistakes, and worked examples.
March 6, 2026qPCR Troubleshooting Guide: 10 Common Problems and Fixes
A practical checklist for diagnosing and fixing the most common qPCR issues, from NTC amplification to unexpected fold changes.