qPCR Efficiency Calculator
Enter the slope of your qPCR standard curve (Ct or Cq plotted against log10 of starting quantity) to calculate the estimated amplification efficiency. This is a calculation from the slope you provide, not a validation of your assay.
Last updated: September 25, 2026
Frequently asked questions
What slope gives 100% efficiency?
A slope of exactly -3.32 (more precisely, -1/log10(2)) corresponds to 100% efficiency, meaning the amount of product doubles every cycle.
Why is a valid slope negative?
In a standard qPCR curve, Ct (or Cq) values decrease as the starting template quantity increases, so slope is normally negative. This calculator flags a positive slope as unlikely to represent a valid standard curve.
What efficiency range is considered acceptable?
Different labs and assay types apply different acceptable ranges, and this varies with reaction chemistry and requirements. This calculator does not set a pass/fail threshold; interpret the result using your own assay's validation criteria.
What can cause efficiency far from 100%?
Common causes include pipetting or dilution errors in the standard curve, PCR inhibitors carried over in the template, suboptimal primer design or concentration, and amplicon secondary structure. Troubleshooting depends on your specific assay.
How is this different from the Annealing Temperature Calculator?
The Annealing Temperature Calculator estimates a PCR cycling parameter from primer melting temperatures, before you generate any data. This tool analyzes the slope from an already-completed standard curve run.
Does this replace laboratory QC procedures?
No. It performs one specific calculation from a slope you provide. Proper assay validation involves replicates, controls, and criteria specific to your laboratory and application.