Free method-validation LOD & LOQ calculator by HPLC or UV-Vis. Enter your System Suitability standard injections and concentration-level area readings in a familiar, Excel-style table — each level calculates its own Average Area and Concentration automatically. Click Calculate to get the calibration curve's Slope, Intercept, r, R², Standard Deviation (σ), and the final LOD and LOQ instantly, with a linearity chart, a pass/fail verdict against the ICH Q2(R2) R² ≥ 0.99 benchmark, a full step-by-step math log, and a built-in Beginner Tips & Guide — no manual calculation needed.
✍️ Developed by Muhammad Asif, Frontend Web Developer|✅ Reviewed by Erum Farooq, Pharmaceutical QC Expert
Determines LOD and LOQ from the calibration curve (regression) built across your concentration levels — the most common ICH Q2(R2) approach.
Formula Used
Concentration = Wt. of Std (mg) × Dilution Factor
Slope (S) = SLOPE(Avg Area, Concentration) | Intercept = INTERCEPT(Avg Area, Concentration)
r = CORREL(Avg Area, Concentration) | R² = r²
σ = STEYX(Avg Area, Concentration) — standard error of the y-estimate
LOD = 3.3 × σ ÷ S | LOQ = 10 × σ ÷ S
Instrument Type
Switches every "Area" label on this page (table headers, results, chart, print report) to "Absorbance". UV-Vis also enforces a valid 0.00–2.00 AU range on every reading — the formula and calculation logic stay identical either way.
Basic Inputs
Weight taken to prepare your working standard
System Suitability — Standard Area
Enter each standard replicate injection reading below (typically 5). Count, Mean, SD and %RSD update live as you type — matching the System Suitability block on the source calculation sheet.
Count = 0 | Mean = – | SD = – | %RSD = –
Concentration Levels & Sample Areas (Excel-Style Table)
Type your own Level label for every row — as many levels as your protocol needs. Click ➕ Add Cell to add one reading column to every level at once, just like inserting a column in Excel. Click ➕ Add Level to add a new row. Each row's Avg Area and Concentration update live as you type.
Levels = 0 | Reading Columns = 0
📊 Results
LOD & LOQ Results
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Slope (S)
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Y-Intercept
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Correlation (r)
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R²
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Std. Deviation (σ)
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LOD
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LOQ
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Linearity Chart — Concentration vs. Avg. Area
Step-by-Step Calculation
1
System Suitability
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2
Dilution Factor, Avg Area & Concentration per Level
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3
Regression — Slope, Intercept, r & R²
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4
Standard Deviation of the Response (σ)
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5
LOD & LOQ
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⚠️ Disclaimer
This calculator is provided for reference and training purposes. Always verify LOD/LOQ results against your validated method, SOP, and applicable pharmacopeial/ICH Q2(R2) requirements before regulatory or release use.
Want the theory?
Beginner Tips & Guide to LOD & LOQ
ICH Q2(R2) background, the regression method explained, acceptance criteria, common mistakes, and a worked example.
Print → Destination → "Save as PDF" — this guarantees the layout, spacing, and margins look exactly like this screen (some printers add their own extra margin on one side, which "Save as PDF" avoids).
Then open More settings and uncheck Headers and footers for a clean file with no browser title/URL/date.
If the report runs onto more than one page, a small "Page X of Y" number is added automatically at the bottom of each page (supported on recent Chrome/Edge versions).
📄 Print Preview — fill in your lab/company details below, then click Print