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qPCR efficiency

Use either a standard-curve slope or two Ct points from a known dilution. A slope of −3.32 is about 100% efficiency; acceptable ranges depend on your assay and lab rules.

Standard curve slope (optional) Dilution factor for two-point mode Ct of less-diluted point Ct of more-diluted point

How qPCR efficiency is calculated

Slope mode: E = 10^(−1/slope) − 1. Two-point mode: E = dilution^(1/(Ct2 − Ct1)) − 1; multiply E by 100 to express efficiency as a percentage. Ct2 must be greater than Ct1, and the dilution factor must be greater than 1.

For example, a tenfold dilution with Ct values of 20 and 23.32 gives approximately 100% efficiency. The two-point result is an estimate, not a substitute for a replicated standard curve across your assay's working range.

Reference: Thermo Fisher Scientific: PCR efficiency and dilution curves. Verify results against your own assay controls and acceptance criteria.