Enter your Blank Measurements, choose a Confidence Level (%) and Detection Probability (%), and this Limit of Detection Calculator tells you the lowest signal your method can reliably distinguish from noise — your LOD — along with the Limit of Blank (LoB), Blank Mean, Blank Standard Deviation, and Number of Samples.
Limit of Detection (LOD)
--
Limit of Blank (LoB)
--
Blank Mean
--
Blank Standard Deviation
--
Number of Samples
--
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.
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.
A 95% confidence level (α = 5%) is most commonly used in analytical chemistry, providing a good balance between statistical rigor and practical application.
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.
Higher detection probability requirements (e.g., 90% vs 50%) result in higher LOD values, representing more stringent criteria for what constitutes a reliable detection.
Yes, this calculator works for any quantitative analytical method including ELISA, PCR, chromatography, spectroscopy, and other techniques that generate blank measurements.
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.
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'.