How this calculator works
A base-10 standard curve relates each tenfold starting-quantity increase to a change in Cq. Its negative slope determines the per-cycle amplification factor. Efficiency is that factor minus one, so ideal doubling is a factor of two and 100% efficiency. Apparent values above 100% can result from inhibitors, pipetting, calibration or non-specific amplification and are not proof of more-than-doubling chemistry.
Formula
Amplification factor = 10^(-1/slope). Efficiency fraction = factor - 1. Slope = -1/log10(1 + efficiency).
Worked example
A slope of -3.3219280949 gives an amplification factor of 2 and efficiency 100%. A 90% efficiency means factor 1.9 and slope about -3.58739760.
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Frequently asked questions
Should the curve use log2 or log10?
This equation uses log10 starting quantity on the horizontal axis and Cq on the vertical axis.
Is amplification factor 2 the same as efficiency 2?
No. Factor 2 means efficiency 1 as a fraction, or 100%.
Does a correct efficiency validate the assay?
No. Specificity, dilution linearity, controls, precision and inhibition must also be assessed.