PCR Efficiency & Copy Number Calculator

Calculate PCR amplification efficiency and copy number from Ct values.

Mode

Slope of standard curve (or Ct₁)

Ct value (or Ct₂) (cycles)

Known copy number at Ct (or reference Ct) (copies or Ct)

Please check your inputs and try again.

Worked Examples

Example 1: Standard curve slope = −3.32

E=(10^(1/3.32)−1)×100

Result: 99.7% efficiency

Near-ideal PCR efficiency

Example 2: ΔΔCt method: ΔCt=2.5 (treatment vs control)

Fold change = 2^(−2.5)

Result: 0.177× or 5.7-fold decrease

Treatment significantly reduces gene expression

Frequently Asked Questions

What is ideal PCR efficiency?

90-110% efficiency means the template is nearly doubling each cycle. Efficiency below 80% suggests inhibitors, primer dimers, or poor primer design. Above 110% suggests non-specific amplification.

What assumptions does ΔΔCt make?

Equal efficiency of target and reference genes (within 5-10%). Linear relationship between Ct and log copy number. Same sample quality across all samples. Validate with standard curve comparison.