Stability Study Design Calculator

Designing a stability study under ICH Q1A(R2) means multiplying out every dimension of the protocol to know exactly how much product you need to put aside, and that's the entire job of this calculator: samples per pull (tests per pull times replicates per test) times time points times storage conditions times batches gives the total test samples required. ICH's own guideline table (§2.1.7.1, General Case) sets those storage conditions as accelerated (40°C ± 2°C/75% RH ± 5% RH), intermediate (30°C ± 2°C/65% RH ± 5% RH), and long-term (25°C ± 2°C/60% RH ± 5% RH, or 30°C ± 2°C/65% RH ± 5% RH depending on climatic zone), and §2.1.3 recommends data from a minimum of three primary batches to capture batch-to-batch variability — both are reflected in the calculator's defaults. On top of the test samples, it adds a retain-sample allowance (a percentage you set, commonly around 10%) for reference material kept aside in case of an out-of-specification result or a need to repeat testing, rounding that allowance up to a whole sample since you can't submit a fractional retain unit.

The grand total is test samples plus retain samples. A rough total sample volume is also estimated by multiplying the grand total by an assumed 5 mL per individual sample — a placeholder for planning bulk drug substance or drug product quantities, since actual sample size varies enormously by dosage form and assay. This calculator handles the arithmetic of study sizing only; it doesn't determine which time points, conditions, or tests your specific product and regulatory region actually require — that comes from your stability protocol and applicable ICH guidance.