qPCR Efficiency Calculator
Calculate the amplification efficiency of your qPCR reaction from the standard curve slope. Validate your experimental setup.
Slope from your qPCR standard curve (typical range: -3.0 to -3.6)
Enter target efficiency to calculate required slope adjustment
What is a good qPCR efficiency value?
Optimal efficiency is 90-110% (1.90-2.10 fold increase per cycle). Efficiency of 100% means perfect doubling each cycle. Values below 90% indicate issues: primer degradation, inhibitors, incorrect annealing temperature, or template degradation. Values above 110% suggest non-specific amplification, primer-dimers, or too-low annealing temperature. Always verify with a standard curve having 3+ points.
How is PCR efficiency calculated from the slope?
Efficiency = (10^(-1/slope) - 1) × 100%. For example: Slope -3.32 gives E = (10^(1/3.32) - 1) = (10^0.301 - 1) = (2 - 1) = 1 = 100%. Another: Slope -3.58 gives E = (10^(1/3.58) - 1) = (10^0.279 - 1) = (1.9 - 1) = 0.9 = 90%. The formula derives from: Ct = -1/slope × log(E) + intercept, solving for E.
Why does my efficiency change between runs?
Variable efficiency comes from: pipetting errors (especially at low template concentrations), instrument calibration drift, master mix age/storage, sample inhibitors, fluorescent dye stability, and ROX reference fluctuations. To minimize variation: use consistent pipetting techniques, prepare master mix in bulk, include ROX normalization, and run triplicates. Store reagents properly and check expiration dates.
How do I improve PCR efficiency?
For low efficiency (<90%): reduce inhibitor effects by diluting templates, redesign primers to avoid GC-rich regions, optimize annealing temperature (gradient PCR), use fresh master mix, check template quality (no degradation). For high efficiency (>110%): increase annealing temperature, design more specific primers, use hot-start polymerases, verify no contamination. Always verify with a standard curve.