Chemistry
Calibration Curve Calculator
Fit a straight line through your standards and read an unknown concentration off it.
Your inputs
Change any value to update the result instantly.
Concentration of the unknown
3.0228
Slope m
0.1095
Intercept b
0.019
R²
0.9997
Before dilution correction
3.0228
Fit quality
Excellent linear fit
Least-squares fit through your four standards. Read an unknown only inside the range of the standards; extrapolating beyond the top standard is unreliable.
What this calculator does
Fits a least-squares straight line through four standards and reads an unknown concentration from it.
What your result means
The concentration of your unknown, with R² showing how well the standards fall on a line.
Measured signal against the fitted line
| Period | Input / invested | Calculated value |
|---|---|---|
| 0 | 0.02 | 0.019 |
| 2 | 0.24 | 0.238 |
| 4 | 0.45 | 0.457 |
| 6 | 0.68 | 0.676 |
Formula and working
y = mx + b; m = Σ(x−x̄)(y−ȳ) / Σ(x−x̄)²; x_unknown = (y − b) / m
- 1
Collect the inputs
Standard 1 concentration = 0; Standard 1 signal = 0.02; Standard 2 concentration = 2; Standard 2 signal = 0.24; Standard 3 concentration = 4; Standard 3 signal = 0.45; Standard 4 concentration = 6; Standard 4 signal = 0.68; Signal of the unknown = 0.35; Dilution factor of the unknown = 1
- 2
Apply the formula
y = mx + b; m = Σ(x−x̄)(y−ȳ) / Σ(x−x̄)²; x_unknown = (y − b) / m
- 3
Result
Concentration of the unknown = 3.0228
Frequently asked questions
Symbols and assumptions
- m
- Slope
- b
- Intercept
- R²
- Coefficient of determination
- • The response is linear over the range of the standards.
- • Standards and unknown were measured the same way.
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • Reading outside the range of the standards is unreliable; a low R² means the calibration must be repeated.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
Report a mistake or request an improvement
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