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USP <71> Sterility Sampling Calculator

Table 2 + Table 3 — articles, mL per medium, and dual-media ×2 rule.

USP <71> uses Table 3 (how many articles to test by batch size and product type) and Table 2 (minimum quantity per culture medium from fill volume). When a container cannot inoculate both media at Table 2 amounts, test twice the Table 3 article count. Test method (membrane filtration vs direct inoculation) is defined in your SOP — it does not change these sampling counts here.

Used for Table 2 minimum quantity per medium and the ×2 article rule.

Results

Articles to test

20

From Table 3

20

Batch tier (Table 3)

More than 500 containers

% of batch tested

0.8%

Table 2 — per medium

5.00 mL

Total test volume

200 mL

Table 2 — 1–40 mL

Half the contents (5.00 mL), not less than 1 mL per medium

Fill volume supports dividing each article between two media (typical FT + SCDM).

USP <71> Table 3 — articles by batch (parenteral)
Articles in batchMinimum articles to test (each medium)*
Not more than 100 containers10% or 4 containers, whichever is greater
More than 100 but not more than 500 containers10 containers
check_circleMore than 500 containers2% or 20 containers, whichever is less

* If one container can inoculate both media at Table 2 quantities, this is the total container count. Otherwise multiply by 2 per USP <71>.

USP <71> Table 2 — minimum quantity per medium (liquids)
Quantity per containerMinimum per medium
Less than 1 mLWhole contents of each container
1–40 mLHalf the contents, not less than 1 mL
Greater than 40 mL and not greater than 100 mL20 mL
Greater than 100 mL10% of contents, not less than 20 mL

Table 3 (parenteral): 2% or 20 containers, whichever is less → 20 article(s). Table 2: Half the contents (5.00 mL), not less than 1 mL per medium. Confirm against your current USP-NF edition, monograph, and SOP before release.

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.

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Related guides

Sterility sampling is compendial math — release is a quality system

USP Chapter 71 defines sterility testing through Table 3 (how many articles to pull by batch size and product type) and Table 2 (minimum quantity per culture medium based on fill volume). For parenterals over 500 containers, the rule is 2% or 20 articles, whichever is less — not the outdated fixed tiers some spreadsheets still use.

When each container cannot supply Table 2 amounts to both media (typical with small fills or whole-container pulls under 1 mL), USP <71> requires twice the Table 3 article count.

This calculator applies both tables for release planning. Pharma Quality Studio carries the narrative: method notes, interpretation memos, OOS playbooks, and PDFs auditors expect.

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