Limit of Quantitation Calculator
Calculate limit quantitation with our free science calculator. Uses standard scientific formulas with unit conversions and explanations.
Formula
LOQ = 10 * SD / Slope | LOD = 3.3 * SD / Slope
LOQ is calculated as 10 times the standard deviation of the blank (or residual SD of regression) divided by the slope of the calibration curve. LOD uses a multiplier of 3.3. These multipliers correspond to approximately 95% and 99% confidence levels respectively per ICH Q2(R1) guidelines.
Worked Examples
Example 1: ICH Standard Deviation Method
Problem: Blank standard deviation is 0.025 absorbance units and the calibration curve slope is 1.5 AU per mg/L. Calculate LOQ and LOD.
Solution: LOQ = 10 * SD / Slope\nLOQ = 10 * 0.025 / 1.5\nLOQ = 0.250 / 1.5 = 0.1667 mg/L\n\nLOD = 3.3 * SD / Slope\nLOD = 3.3 * 0.025 / 1.5\nLOD = 0.0825 / 1.5 = 0.0550 mg/L
Result: LOQ: 0.1667 mg/L | LOD: 0.0550 mg/L | LOQ/LOD Ratio: 3.03
Example 2: Calibration Curve Regression Method
Problem: Five calibration standards give concentrations [0.1, 0.2, 0.5, 1.0, 2.0] mg/L and responses [0.15, 0.30, 0.75, 1.50, 3.00] AU. Calculate LOQ from residual standard deviation.
Solution: Linear regression: y = 1.5x + 0.0\nResidual standard deviation (Sy/x) from regression residuals\nLOQ = 10 * Sy/x / Slope\nLOD = 3.3 * Sy/x / Slope\nR-squared is near 1.000 indicating excellent linearity
Result: LOQ and LOD calculated from regression residuals with R-squared near 1.0
Frequently Asked Questions
What is the Limit of Quantitation (LOQ) and how does it differ from Limit of Detection (LOD)?
The Limit of Quantitation (LOQ) is the lowest concentration of an analyte in a sample that can be determined with acceptable precision and accuracy under stated experimental conditions. It differs from the Limit of Detection (LOD), which is the lowest concentration that can be reliably detected but not necessarily quantified. According to ICH guidelines, LOD is calculated as 3.3 times the standard deviation of the blank divided by the slope of the calibration curve, while LOQ uses a multiplier of 10 instead of 3.3. This means the LOQ is approximately three times higher than the LOD. The LOQ represents the practical lower boundary for reporting a numerical concentration value with confidence.
How do I get the most accurate result?
Enter values as precisely as possible using the correct units for each field. Check that you have selected the right unit (e.g. kilograms vs pounds, meters vs feet) before calculating. Rounding inputs early can reduce output precision.
Is Limit of Quantitation Calculator free to use?
Yes, completely free with no sign-up required. All calculators on NovaCalculator are free to use without registration, subscription, or payment.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.
Does Limit of Quantitation Calculator work offline?
Once the page is loaded, the calculation logic runs entirely in your browser. If you have already opened the page, most calculators will continue to work even if your internet connection is lost, since no server requests are needed for computation.
What formula does Limit of Quantitation Calculator use?
The formula used is described in the Formula section on this page. It is based on widely accepted standards in the relevant field. If you need a specific reference or citation, the References section provides links to authoritative sources.