qPCR Efficiency Calculator
Use our qPCR efficiency calculator to calculate qPCR efficiency from a standard curve slope. Includes qPCR explained, what is qPCR efficiency, the qPCR efficiency formula, qPCR efficiency calculation steps, and practical tips on how to improve qPCR efficiency.
qPCR Explained: What is qPCR Efficiency?
qPCR (quantitative PCR), also called real-time PCR, measures DNA amplification as it happens by tracking fluorescence across cycles. It’s commonly used for gene expression studies, pathogen detection, and DNA quantification.
qPCR efficiency describes how well a target sequence amplifies each cycle. In an ideal reaction, the amount of product doubles every cycle (100% efficiency).
This qPCR efficiency calculator helps you calculate qPCR efficiency from a standard curve slope (Ct vs log concentration), which is the most common qPCR efficiency calculation approach.
qPCR Efficiency Formula
Efficiency is typically calculated from the slope of the standard curve built from serial dilutions.
A slope of about −3.32 corresponds to ~100% efficiency.
At 100% efficiency, amplification per cycle is 2×.
A slope near −3.32 is the classic target for ~100% efficiency.
Less negative slope generally indicates higher amplification factor (up to a point).
How to Use the qPCR Efficiency Calculator
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Enter the slope from your qPCR standard curve (Ct vs log10 concentration).
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The calculator applies the qPCR efficiency formula: E(%) = (10^(-1/slope) − 1) × 100.
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Review the efficiency percentage and the amplification factor per cycle.
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If efficiency is outside the typical target range, use the troubleshooting tips below to improve qPCR efficiency.
Frequently Asked Questions
qPCR efficiency is how effectively your PCR amplifies the target each cycle. 100% efficiency means the target doubles every cycle (2× amplification per cycle).
Most commonly from the standard curve slope using E(%) = (10^(-1/slope) − 1) × 100.
A slope around −3.32 corresponds to ~100% efficiency (about 2× amplification per cycle).
E(%) = (10^(-1/slope) − 1) × 100, where slope comes from Ct vs log10 input amount.
Many workflows aim for roughly 90%–110% efficiency, but what’s acceptable depends on your assay and validation requirements.
Common improvements include optimizing primer design (avoid dimers, match Tm), adjusting annealing temperature, improving template quality (remove inhibitors), optimizing Mg2+ / buffer conditions, and verifying dilution series accuracy for the standard curve.
qPCR measures amplification in real time using fluorescence and provides quantitative information (like Ct values), while traditional PCR is typically endpoint detection.
It often indicates issues like primer-dimers, non-specific amplification, pipetting/dilution errors in the standard curve, or fluorescence artifacts.