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qPCR Calculator

Turn raw qPCR Ct values into relative gene expression, or check how efficient your primers are. Use the ΔΔCt mode to compare a treated sample with a control against a reference gene, and the efficiency mode after running a dilution series.

Enter your Ct values to find the fold change in gene expression with the ΔΔCt method, or the slope of your standard curve to check your primer efficiency.

What do you want to calculate?

Enter 1 to 3 technical replicates for each; we use their mean. Replicates more than 0.5 cycles apart are flagged.

Control sample

Target gene Ct
Reference gene Ct

Treated sample

Target gene Ct
Reference gene Ct
Enter your Ct values and press Calculate to see the fold change.

How it's calculated

ΔCt = Ct(target) − Ct(reference)

ΔΔCt = ΔCt(treated) − ΔCt(control)

Fold change = 2^−ΔΔCt

Primer efficiency = (10^(−1 ÷ slope) − 1) × 100%

Replicate Ct values are averaged first. The 2^−ΔΔCt method (Livak & Schmittgen, 2001) assumes both primer pairs are close to 100% efficient, which corresponds to a standard-curve slope of about −3.32; 90–110% is generally accepted.