Can I solve for different variables?

Yes! This calculator supports reverse solving. You can solve for: Standard-curve slope, Amplification factor (per cycle), Amplification efficiency (%).

qPCR Efficiency Calculator

Convert standard-curve slopes into amplification efficiency and fold-increase per cycle.

Formula shown1 inputs definedUpdated Nov 2025By CalcuTotal TeamFree, no sign-up

Quick Summary

Use this when you need:

Check whether a qPCR assay's slope stays within MIQE-recommended bounds
Convert a reported efficiency back into the slope needed for assay validation
Explain to teammates how a shallow slope lowers amplification per cycle

You’ll need:Standard-curve slope

You’ll get:Amplification factor (per cycle), Amplification efficiency (%)

How this is calculated

Formula:

amplification_factor = 10 ** (-1/slope); efficiency_pct = (amplification_factor - 1) * 100

In plain language:

Using the qPCR standard curve relationship, we take the negative reciprocal of the slope to compute the per-cycle fold change, then convert that into percent efficiency relative to a perfect doubling.

The formula is always visible so you can verify the math and explain your numbers to anyone who asks.

What these terms mean

Standard-curve slope

Standard-curve slope used in the calculation.

Amplification factor (per cycle)

Amplification factor (per cycle) used in the calculation.

Amplification efficiency (%)

Amplification efficiency (%) used in the calculation.

When to use this calculator

Check whether a qPCR assay's slope stays within MIQE-recommended bounds
Convert a reported efficiency back into the slope needed for assay validation
Explain to teammates how a shallow slope lowers amplification per cycle

Last updated: November 19, 2025

qPCR efficiency calculator explained

Standard curve slopes describe how many PCR cycles it takes to cover tenfold changes in template concentration. This calculator turns that slope into the per-cycle amplification factor and percent efficiency so you can verify that assays fall within the MIQE-recommended 90-110% range.

How the conversion works

For a standard curve slope $m$ (Ct versus log₁₀ concentration), the per-cycle fold amplification ( $F$ ) is

F = 10^{-1/m}

Efficiency is the percentage by which $F$ exceeds 1:

E\\% = (F - 1) \\times 100

Rearranging gives $m = -1 / \\log_{10}(F)$ when you know the desired efficiency.

Units and conversions

Quantity	Units	Notes
Slope $m$	Ct/log decade	Perfect doubling yields -3.32.
Amplification factor $F$	fold	$F = 2$ at 100% efficiency.
Efficiency $E\\%$	percent	$(F - 1) \\times 100$ .

Worked examples

Ideal assay
$m = -3.32$ :

F = 10^{-1/(-3.32)} = 2.00 \\Rightarrow E = 100\\%

Suboptimal slope
$m = -3.60$ :

F = 10^{-1/(-3.60)} = 1.895,\\quad E = (1.895 - 1) \\times 100 = 89.5\\%

Tips and pitfalls

Keep slopes within -3.1 to -3.6; steeper slopes (<-3.6) indicate poor amplification or inhibitors.
Build standard curves with at least five points spanning four logs to minimize slope error.
Monitor $R^2$ values alongside efficiency; MIQE guidelines require $R^2 \\ge 0.99$ for validated assays.
Use fresh dilutions for each run; pipetting drift across serial dilutions is a common source of slope variation.

References and further reading

Frequently Asked Questions

Medical Disclaimer

This calculator is for informational and educational purposes only and should not be considered medical advice.

The results provided are estimates based on the information you enter and should not be used as a substitute for professional medical advice, diagnosis, or treatment.

Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have calculated here.

If you think you may have a medical emergency, call your doctor or emergency services immediately.

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Calculator info

Version:: v1.0.0
Last reviewed:: Nov 15, 2025
Sensitivity:: high
References:: 2

High-sensitivity calculator

This calculator involves important decisions. Results are for informational purposes only. Verify results independently for critical applications.

Last updated: November 19, 2025

qPCR efficiency calculator explained

How the conversion works

For a standard curve slope $m$ (Ct versus log₁₀ concentration), the per-cycle fold amplification ( $F$ ) is

F = 10^{-1/m}

Efficiency is the percentage by which $F$ exceeds 1:

E\\% = (F - 1) \\times 100

Rearranging gives $m = -1 / \\log_{10}(F)$ when you know the desired efficiency.

Units and conversions

Quantity	Units	Notes
Slope $m$	Ct/log decade	Perfect doubling yields -3.32.
Amplification factor $F$	fold	$F = 2$ at 100% efficiency.
Efficiency $E\\%$	percent	$(F - 1) \\times 100$ .

Worked examples

Ideal assay
$m = -3.32$ :

F = 10^{-1/(-3.32)} = 2.00 \\Rightarrow E = 100\\%

Suboptimal slope
$m = -3.60$ :

F = 10^{-1/(-3.60)} = 1.895,\\quad E = (1.895 - 1) \\times 100 = 89.5\\%

Tips and pitfalls

Keep slopes within -3.1 to -3.6; steeper slopes (<-3.6) indicate poor amplification or inhibitors.
Build standard curves with at least five points spanning four logs to minimize slope error.
Monitor $R^2$ values alongside efficiency; MIQE guidelines require $R^2 \\ge 0.99$ for validated assays.
Use fresh dilutions for each run; pipetting drift across serial dilutions is a common source of slope variation.

Quick Summary

Calculator Tool

How this is calculated

What these terms mean

Standard-curve slope

Amplification factor (per cycle)

Amplification efficiency (%)

When to use this calculator

qPCR efficiency calculator explained

How the conversion works

Units and conversions

Worked examples

Tips and pitfalls

References and further reading

Frequently Asked Questions

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Medical Disclaimer

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Calculator info

qPCR efficiency calculator explained

How the conversion works

Units and conversions

Worked examples

Tips and pitfalls

References and further reading

Frequently Asked Questions

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