How to use (3 steps)
- Paste standard points (Quantity, Ct) or load a CSV file. Rows with the same Quantity are treated as replicates.
- Choose a regression method (OLS/WLS) and options such as 95% bands. Enter unknown Ct values if you have them.
- Click Calculate to see the standard curve, efficiency, QC checks, unknown estimates, and step log. Share URLs keep the same settings.
Recommended order
- First, build a standard curve (this calculator)
- Next, review PCR efficiency (%) → Jump to efficiency
- If needed, calculate relative expression (ΔCt / ΔΔCt) → ΔCt / ΔΔCt
Go deeper
- Linear regression & correlation
How to read residuals and 95% bands
- Descriptive stats
Check replicate variability
Data input and options
Results (summary)
PCR efficiency (%)
Calculated from slope m as Efficiency = (10^(-1/m) - 1) × 100. The range shown is a guide.
Initial results use the preset standard curve; paste your own data and calculate to replace them.
| n (points) | 15 |
|---|---|
| k (levels) | 5 |
| slope m | -3.32 |
| intercept b | 38.24 |
| R² | 1 |
| efficiency (%) | 100.1 |
Ranges are guides. For research/education, review standard points and residuals together.
Quality checks (guide)
Concentration levels (mean ± SD)
| Quantity | log10Q | n | Ct_mean | Ct_SD |
|---|---|---|---|---|
| 1e+7 | 7 | 3 | 15 | 0.03 |
| 1e+6 | 6 | 3 | 18.32 | 0.03 |
| 100000 | 5 | 3 | 21.64 | 0.03 |
| 10000 | 4 | 3 | 24.96 | 0.03 |
| 1000 | 3 | 3 | 28.28 | 0.03 |
Standard points (fit rows)
Advanced columns (weight / yhat / residual / leverage / cooksD) can be toggled.
| Quantity | log10Q | Ct | weight | yhat | residual | leverage | cooksD |
|---|---|---|---|---|---|---|---|
| 1e+7 | 7 | 14.97 | 1 | 15 | -0.03 | 0.2 | 0.203125 |
| 1e+7 | 7 | 15 | 1 | 15 | 0 | 0.2 | 0 |
| 1e+7 | 7 | 15.03 | 1 | 15 | 0.03 | 0.2 | 0.203125 |
| 1e+6 | 6 | 18.29 | 1 | 18.32 | -0.03 | 0.1 | 0.080247 |
| 1e+6 | 6 | 18.32 | 1 | 18.32 | 0 | 0.1 | 0 |
Unknown samples (Ct → Quantity)
| Sample | Ct | log10Q_hat | Quantity_hat | DF | Quantity_corrected |
|---|---|---|---|---|---|
| U1 | 20 | 5.493976 | 311871.654 | 1 | 311871.654 |
| U2 | 23.5 | 4.439759 | 27527.0097 | 1 | 27527.0097 |
Standard curve and residuals
Calculation steps (How it’s calculated)
Notes for educators
- Switch OLS/WLS and intercept on/off to compare how slope, residuals, and QC guides change.
- With replicates, the mean and SD per level help discuss variability, outliers, and weighting.
FAQ
What is a qPCR standard curve?
A curve that relates standard quantity (copy number or concentration) to Ct by fitting Ct vs log10(quantity). It helps check linearity (R²) and amplification efficiency.
How many standard points are required?
At least two points are required to fit a line. For linearity and outlier checks, 4–6 points are recommended.
How is PCR efficiency (%) calculated?
From slope m: Efficiency = (10^(-1/m) - 1) × 100. The displayed range is a guide.
What does a slope around -3.32 indicate?
For a 10× dilution series, a slope near -3.32 corresponds to an apparent efficiency of about 100% (ideal guide).
Can efficiency exceed 100%?
Because it is inferred from the slope, apparent values over 100% can occur due to dilution error or inhibition. Treat it as a guide and check residuals and standard points.
Does the share URL include data?
Only settings (methods and band options) are saved. Standard and unknown data are not included.
What unit should I use for Quantity?
Any unit is fine (copy number, ng, concentration). Quantity must be positive for log10.
Related tools
References (notes)
Guides shown on this calculator are general references. For research/education, consult primary sources as needed.
Comments
Share questions or improvements (comments load after you click the button).