Limit of Detection Calculator

The Limit of Detection (LOD) Calculator determines the lowest concentration of a substance that a measurement method can reliably distinguish from background noise — a critical threshold in lab testing, environmental analysis, and clinical diagnostics. Enter your blank measurements (at least 20 values), set your confidence level and detection probability, and select a measurement unit to calculate your Limit of Detection. Secondary outputs include the Limit of Blank (LoB), blank mean, and blank standard deviation. Also try the Arterial Blood Gas (ABG) Calculator.

Enter at least 20 blank measurement values separated by commas

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Typically 95% for α = 5%

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Required detection probability for LOD calculation

Results

Limit of Detection (LOD)

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Limit of Blank (LoB)

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Blank Mean

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Blank Standard Deviation

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Number of Samples

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Frequently Asked Questions

What is the difference between LOD and LoB?

The Limit of Blank (LoB) is the highest measurement result likely to be observed for a blank sample, while the Limit of Detection (LOD) is the lowest analyte concentration likely to be reliably distinguished from the LoB. See also our Calibration Curve Calculator (Analytical).

How many blank measurements do I need for accurate LOD calculation?

A minimum of 20 blank measurements is recommended for reliable statistical analysis, though 60 or more blank measurements provide better precision according to CLSI EP17-A2 guidelines.

What confidence level should I use for LOD calculations?

A 95% confidence level (α = 5%) is most commonly used in analytical chemistry, providing a good balance between statistical rigor and practical application.

Why is LOD important in analytical method validation?

LOD establishes the lowest concentration that can be reliably detected by an analytical method, which is crucial for determining method sensitivity and ensuring reliable results in clinical and research applications. You might also find our GC Retention Index Calculator useful.

How does detection probability affect LOD calculation?

Higher detection probability requirements (e.g., 90% vs 50%) result in higher LOD values, representing more stringent criteria for what constitutes a reliable detection.

Can I use this calculator for any type of analytical method?

Yes, this calculator works for any quantitative analytical method including ELISA, PCR, chromatography, spectroscopy, and other techniques that generate blank measurements.

What should I do if my blank measurements show high variability?

High variability in blanks may indicate method instability or contamination issues. Consider investigating and resolving the source of variability before calculating LOD, or increase the number of blank measurements.

How do I interpret the calculated LOD value?

The LOD represents the minimum concentration you can confidently detect above background noise. Samples with concentrations below the LOD should be reported as 'not detected' or '< LOD'.