Analytical Method Validation — ICH Q2
Precision (%RSD) Calculator
Enter replicate results to calculate mean, standard deviation, and %RSD — the core statistic used to assess repeatability and intermediate precision.
Why %RSD Matters
Precision — the agreement among repeated measurements of the same sample under defined conditions — is one of the core ICH Q2 validation parameters for assay and impurity methods. It's most commonly expressed as the Relative Standard Deviation (%RSD), also called the coefficient of variation.
Typical Acceptance Criteria
| Test Type | Common %RSD Acceptance |
|---|---|
| Assay (HPLC, potency) | ≤ 1.0% – 2.0% (method/product dependent) |
| Impurities near reporting threshold | ≤ 5.0% – 10.0% (wider due to low signal) |
| Content uniformity | Per compendial acceptance value (AV) approach, not %RSD alone |
| System suitability (replicate injections) | ≤ 1.0 – 2.0% typical, per method |
Always use your method's own validated/compendial acceptance criteria — the values above are common industry benchmarks, not universal requirements.
Interactive Calculator
Notes on Using This Calculator
- For repeatability, use replicates from the same analyst, instrument, and day.
- For intermediate precision, pool results across different analysts, days, or instruments, and evaluate %RSD across the combined dataset.
- A low %RSD with very few replicates (e.g., n = 2–3) provides weaker evidence than the same %RSD with n = 6–9 — follow ICH Q2 minimum replicate recommendations.
This tool is for educational and preliminary assessment purposes. Final precision conclusions must follow your approved validation protocol's statistical methodology and pre-defined acceptance criteria.
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