LOD/LOQ Calculator
Determine the sensitivity limits of on-chip immunoassays, ELISA and biosensor measurements. Calculate LOD and LOQ from blank replicates or calibration curve data.
Method & Data
Enter values separated by commas or newlines
Minimum 2 replicates required. Enter blank signal values (absorbance, fluorescence, etc.)
Results
| Mean Blank Signal | 0.0600 |
| Standard Deviation (SD) | 0.0158 |
| Number of Replicates | 5 |
Understanding LOD and LOQ
Limit of Detection (LOD)
The lowest concentration of a substance that can be reliably detected by an analytical method. At the LOD, the measured signal is distinguishable from the background noise. Typically defined as: LOD = mean_blank + 3 × SD_blank or LOD = 3 × Sy/x / slope for calibration curves. Below the LOD, results are unreliable and should not be used for quantification.
Limit of Quantification (LOQ)
The lowest concentration at which a substance can be quantified with acceptable accuracy and precision. The LOQ is higher than the LOD and is typically defined as: LOQ = mean_blank + 10 × SD_blank or LOQ = 10 × Sy/x / slope for calibration curves. Results between LOD and LOQ should be reported with a qualifier indicating reduced precision.
Blank-Based Method
This approach uses replicate measurements of a blank sample (no analyte) to estimate the variability of the assay. The blank SD reflects instrumental and methodological noise. This method works best for assays with low baseline signal and is common in immunoassays and biosensors.
Calibration Curve Method
This approach performs linear regression on calibration data (multiple concentration-response pairs) and uses the standard error of the regression (Sy/x) to calculate LOD and LOQ. This method accounts for the variance across the entire calibration range and is suitable for assays with strong linear response (R² > 0.95).
Microfluidics Context
Microfluidic devices enable miniaturized immunoassays, ELISA platforms, and label-free biosensors with reduced reagent consumption and faster analysis times. Determining accurate LOD and LOQ is critical for validating on-chip assays and ensuring they meet clinical or research requirements. Microfluidic geometries can affect background noise and signal uniformity, directly impacting detection limits.
Complement your analysis with more tools
For full 4PL curve fitting and sample interpolation, try our Assay Analyser — the perfect companion to LOD/LOQ validation.