qPCR Efficiency Calculator
Determine the efficiency of your qPCR assay. Enter the slope obtained from your standard curve to find the percent efficiency and fold amplification per cycle.
Standard Curve Slope
Enter the slope of the linear regression line of Ct vs. log(concentration).
Amplification Efficiency
Expert Tip
An efficiency > 100% (slope flatter than -3.32) usually suggests pipetting errors or template/primer contamination, whereas an efficiency < 90% indicates PCR inhibitors or poor primer design.
Methodology & Equations
The Efficiency Equation
The amplification efficiency (E) and factor of replication are calculated from standard curve slopes using:
Ideal Values
- **Ideal Slope:** -3.32 (100% efficiency, double templates every cycle).
- **Acceptable Slope Range:** -3.58 to -3.10 (corresponding to 90% to 110% efficiency).
- **Linear Correlation Coefficient (R²):** Should be ≥ 0.99 for a reliable standard curve.
How to Calculate qPCR Efficiency: Step-by-Step
Below is a step-by-step example using a standard curve slope of -3.40:
Calculate the Exponent
Divide -1 by the slope.
Example: -1 / -3.40 = 0.2941.
Calculate the Amplification Factor
Raise 10 to the power of the exponent.
Example: 100.2941 = 1.968. This means the target sequence increases by 1.968-fold with each cycle.
Calculate Percent Efficiency
Subtract 1 from the factor and multiply by 100.
Example: (1.968 - 1) × 100 = 96.8%.
Related Calculators
View All Biology Tools →DNA Copy Number Calculator
Calculate the number of DNA template copies from mass and length.
PCR Master Mix Calculator
Calculate reaction component volumes for PCR experiments.
DNA/RNA Melting Temperature Calculator
Calculate the melting temperature (Tm) for primers.