MAXScanner biology & lab calculator
qPCR Efficiency Calculator — Standard Curve, Slope, R² & Residuals
Calculate qPCR amplification efficiency from a slope or fit a complete Ct/Cq versus template standard curve. Get slope, intercept, R², efficiency, amplification factor and point-by-point residuals.
Fit your standard curve
One row per standard: template amount, Ct/Cq. Amount can be copies, concentration or relative quantity, but must stay in one consistent scale.
Slope → efficiency quick solve
Formula: E% = (10^(-1/slope) - 1) × 100. Treat quality thresholds as assay-context guidance, not a substitute for your protocol or validation criteria.
Point-by-point residual audit
| Amount | log₁₀ amount | Measured Ct/Cq | Predicted | Residual |
|---|---|---|---|---|
| 1000000 | 6.0000 | 15.2 | 15.200 | -0.000 |
| 100000 | 5.0000 | 18.5 | 18.500 | 0.000 |
| 10000 | 4.0000 | 21.8 | 21.800 | 0.000 |
| 1000 | 3.0000 | 25.1 | 25.100 | 0.000 |
| 100 | 2.0000 | 28.4 | 28.400 | 0.000 |
How this standard-curve calculator works
Paste template amount and measured Ct/Cq for each standard. The calculator takes log₁₀ of each positive template amount, fits an ordinary least-squares line, then derives amplification efficiency from its slope. Unlike a slope-only widget, it keeps R², intercept, predicted Ct/Cq and every residual visible so you can inspect the curve rather than trusting one headline percentage.
Useful workflow
Plan standards with the serial dilution calculator, convert DNA concentration to molecular copies when needed, then paste the measured standard series here. Keep units consistent across all template amounts.
FAQs
How is qPCR efficiency calculated from slope?
Efficiency is (10^(-1/slope)-1)×100%. A slope near -3.322 corresponds to approximately 100% amplification efficiency.
Can I calculate the slope and R² from my dilution series?
Yes. Paste at least three template amount and Ct/Cq pairs. The calculator log10-transforms positive template amounts and fits Ct/Cq against log10(template) by ordinary least squares.
Why show residuals?
Residuals show how far each measured Ct/Cq lies from the fitted standard curve, making an unusual dilution point easier to spot without hiding it.