100
%
1.99997
x per cycle
-0
%
6.9
cycles
1,000,000,000
fold
0.999
100
%
1.99997
x per cycle
-0
%
6.9
cycles
1,000,000,000
fold
0.999
The PCR Efficiency Calculator converts the slope of a qPCR standard curve into a percent efficiency value. PCR efficiency is a critical quality metric that indicates how well the amplification reaction is performing. An ideal PCR reaction doubles the target with each cycle (100% efficiency), corresponding to a standard curve slope of -3.322. This calculator helps you quickly evaluate whether your qPCR assay meets the 90-110% efficiency criteria required for reliable quantification.
PCR efficiency is calculated from the slope of the log(copy number) vs. Ct standard curve:
Efficiency (%) = (10^(-1/slope) - 1) × 100
Key relationships:
Efficiency below 90% may indicate primer dimers, suboptimal primer design, or inhibitors. Efficiency above 110% may indicate non-specific amplification or pipetting errors.
Inputs
Results
A slope of -3.32 yields approximately 100% efficiency with an amplification factor of 2.0, indicating the target doubles each cycle.
Inputs
Results
A slope of -3.80 gives only 83.4% efficiency. This is below the acceptable range and the assay should be optimized.
The MIQE guidelines recommend a PCR efficiency between 90% and 110%, corresponding to a standard curve slope between -3.6 and -3.1. Efficiencies within this range are considered reliable for quantitative analysis. The R² value of the standard curve should also be ≥0.98, indicating good linearity across the dilution series.
Low efficiency (<90%) can result from: (1) suboptimal primer design — check for secondary structures, high GC content, or inappropriate Tm; (2) PCR inhibitors in the template — humic acids, hemoglobin, or extraction reagent carryover; (3) degraded reagents — old dNTPs or polymerase; (4) primer dimers competing with target amplification; (5) suboptimal annealing temperature.
True biochemical efficiency cannot exceed 100%. Apparent efficiencies above 110% typically indicate non-specific amplification (primer dimers or off-target products), pipetting errors in the standard curve dilutions, or template inhibition at high concentrations that artificially steepens the slope. Run a melt curve analysis to check for non-specific products.
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