Free · Laboratory calculations

qPCR Standard-Curve Efficiency & Amplification Factor

Convert a negative standard-curve slope to amplification factor and apparent qPCR efficiency, or recover slope from the factor.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

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Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

An amplification factor of 2 corresponds to 100% efficiency and a standard-curve slope of approximately −3.321928. The percentage is the factor minus one, multiplied by 100.

A = 10^(−1/slope); efficiency = 100 × (A − 1)%

Worked example

Enter these known values and leave the other values blank.

Amplification factor per cycle A
2
Cq versus log₁₀ starting quantity: slope
-3.322
Apparent amplification efficiency
100 %

Assumptions and limitations

  • The standard curve plots Cq against the base-10 logarithm of starting quantity. Another axis convention requires a different interpretation.
  • Slope is negative for this amplification model. A zero slope is singular, and an amplification factor of one has no finite inverse slope.
  • Apparent efficiency above 100% is shown rather than clipped. It is an algebraic result from the curve and may indicate that the measurement or model needs investigation.
  • Efficiency is a read-only percentage output. Factor and slope are editable inverse inputs.

Common questions

Is amplification factor 2 the same as 200% efficiency?

No. A factor of 2 includes the original amount plus a 100% increase, so efficiency is 100%.

Why can an apparent value exceed 100%?

The formula reports the value implied by the entered curve. It does not establish that the experiment truly produces more than a doubling each cycle.

References

Bookify requires a negative standard-curve slope, amplification factor above one and positive apparent efficiency.

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