Enter your Standard Concentrations and Standard Measurements to build a linear calibration curve, then plug in your Unknown Sample Measurements to back-calculate their concentrations — the calculator returns your Linear Equation, Slope, Y-Intercept, and R² value so you can immediately judge how well your standards fit the line.
R² (Correlation Coefficient)
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Slope
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Y-Intercept
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Linear Equation
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A calibration curve is a graph that shows the relationship between known concentrations and their corresponding measurements (like absorbance or fluorescence). It's essential for determining unknown concentrations by establishing a mathematical relationship through linear regression.
Use standards that span the expected concentration range of your unknown samples. Include at least 5-6 data points, with a blank (zero concentration) and ensure standards are prepared accurately using the same conditions as your unknowns.
R² (correlation coefficient) indicates how well your data fits a straight line. Values closer to 1.000 indicate better linearity. Generally, R² values above 0.95 are considered acceptable for most analytical applications.
Poor linearity (low R²) may indicate measurement errors, improper standard preparation, instrument drift, or that your analyte doesn't follow linear response over the concentration range tested. Check your standards and consider using a smaller concentration range.
Yes, this calculator works with any measurement that has a linear relationship with concentration, including absorbance (UV-Vis), fluorescence, chromatography peak areas, or any other quantitative analytical signal.
A minimum of 5 standards is recommended, including a blank. More points generally improve reliability, but 6-8 well-distributed standards across your concentration range typically provide excellent results for most applications.
Extrapolation beyond your calibration range is unreliable and should be avoided. Either dilute samples with high measurements or concentrate samples with low measurements to bring them within your calibrated range.