Pharmaceutics

Content Uniformity Calculator

Checks whether a batch of tablets or capsules passes the USP <905> content uniformity test, from the assay of each individual unit.

Acceptance value (AV)

Enter at least 10 unit contents greater than zero — 0 entered so far.

Unit data entry

Assay result of each unit, in the same unit as the label claim (mg, or % of label).

Label claim (mg or %)

Reference value for percentage calculations — the labelled amount per unit, or 100 if the results are already % of label.

Individual unit contents

Unit 1

Unit 2

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Unit 10

Try an example (label claim 100)

AV = |M − X̄| + k·s

M = reference value (98.5–101.5% of label claim), X̄ = sample mean, k = 2.4 (for n=10), s = sample standard deviation.

M depends on where the mean falls: if X̄ is between 98.5% and 101.5% of the label claim, M = X̄ and only the spread counts; below 98.5%, M = 98.5% of label; above 101.5%, M = 101.5% of label. The standard deviation uses n − 1, and RSD = s ÷ X̄ × 100.

Each unit is also expressed as a percentage of the label claim and must fall within 85–115%. A batch passes Stage 1 when AV ≤ 15.0 and every unit is within that range.

References

United States Pharmacopeia–National Formulary. General Chapter <905> Uniformity of Dosage Units. Rockville (MD): USP.

Common questions

k is the acceptability constant from USP <905>. It is 2.4 when 10 units are tested and 2.0 when 30 are tested; this calculator uses 2.4 whatever number of units you enter.

Yes. When the mean sits between 98.5% and 101.5% the first term is zero, but a large standard deviation still pushes AV up — a batch with the right average but widely scattered units fails.

The labelled amount per unit, in the same unit as your assay results — for example 250 for 250 mg tablets assayed in mg. If your results are already expressed as % of label, leave it at 100.

USP allows a second stage: 20 more units are tested and all 30 are evaluated together, with a limit of AV ≤ 25.0, at least 24 units within 85–115% and none outside 75–125%.

No. Weight variation infers drug content from each unit's weight and is allowed only in limited cases (for example, high-dose tablets). Content uniformity measures the drug in each unit directly by assay.

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