Multi-point Calibration Calculator

Understanding Calibration

What is Calibration?

Calibration is the process of comparing your instrument's measurements to known standard values. It's like using a ruler to check if your measuring tape is accurate - but for laboratory instruments.

Why Multi-point Calibration?

Multi-point calibration offers several advantages over single-point calibration:

  • Verifies linearity across your method's entire measuring range
  • Identifies systematic errors at different concentrations
  • Provides more reliable results across different concentration levels
  • Meets regulatory requirements for method validation
Thompson, M. & Ellison, S. L. R. Fitness for purpose of analytical methods: A laboratory guide to method validation and related topics. Eurachem Guide (2014).

How to Use This Calculator

  1. 1 Enter your standard values (known concentrations)
  2. 2 Enter your measured values (instrument readings)
  3. 3 Click "Calculate" to get your results
  4. 4 Review the calibration curve and statistics

Quick Tips

Best Practices
  • Use at least 5 calibration points for robust results
  • Space your calibration points evenly across your working range
  • Include concentrations at the lower and upper limits of your range
  • Analyze standards from lowest to highest concentration
Common Pitfalls
  • Avoid extrapolating beyond your calibration range
  • Don't ignore outliers without investigation
  • Remember that R² alone doesn't guarantee accuracy

Practice Examples

Glucose Analysis

Clinical chemistry calibration (2-15 mmol/L)

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Heavy Metal Analysis

Environmental testing (0-500 μg/L)

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Protein Assay

Bradford assay (0-2000 μg/mL)

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Calculator

Interpreting Your Results

Key Parameters
  • Slope: Should be close to 1.0 for a well-calibrated system. Significant deviation suggests proportional bias.
  • Y-intercept: Should be close to 0. Deviation indicates constant bias.
  • R²: Measures linearity. Values closer to 1.0 indicate better linearity.
Acceptance Criteria

Common acceptance criteria include:

  • R² ≥ 0.995 for most analytical methods
  • Relative difference typically ≤ 10% at each level
  • Slope between 0.9 and 1.1
  • Y-intercept not significantly different from zero
ISO/IEC 17025:2017 General requirements for the competence of testing and calibration laboratories