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Reserve Sample Calculator (21 CFR 211.170)

2× release test consumption — reserve quantity from batch size and test units.

Estimate reserve sample quantity under 21 CFR 211.170 — at least twice the units consumed by all required release tests. Auto-fills sterility units from USP <71> when batch size is known.

Assay, identity, water, particulate, etc.

Results

Minimum reserve

80 units

Release test total

40 units

% of batch

3.3%

Rule

2× release tests

Retain at least 80 unit(s) — twice the 40 unit(s) consumed by release testing (3.3% of this batch). Store in the same container-closure system (or equivalent), label as reserve, and follow 21 CFR 211.170 and your SOP for location and retention period.

infoCompendial planning aid. Compendial planning aid only — not a substitute for your validated SOP, pharmacopeial edition in force, regulatory submission, or qualified-person release decision. Always verify sampling tables against the official USP-NF (or applicable pharmacopeia) and your quality system before testing or batch disposition.

Need expert help?

Document reserve samples in Pharma Quality Studio

Pharma Quality Studio helps you tie reserve quantity to batch records, storage location, and retention policy — audit-ready with Melody.

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Reserve samples are regulatory insurance — quantity is rule-based

21 CFR 211.170 requires reserve samples of sufficient quantity to perform at least twice all required release tests. That means summing sterility, assay, identity, and every other test that consumes product.

Planners often underestimate when sterility tiers jump at batch boundaries — pairing this with USP <71> math keeps reserve pulls accurate.

This calculator gives the minimum count. Pharma Quality Studio documents where reserves are stored, who labeled them, and how long you retain them.

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