AQL ChartAQL 4.0: sample sizes and accept/reject numbers by lot size
Find your lot size in the first column, then read across to your general inspection level. Each cell gives the sample size to inspect, with Ac and Re in brackets. The code letter for each level comes from Table I, and because of the arrows in Table II-A, the plan used can belong to a different code letter from the row's own (see the code letters page).
AQL 4.0 at general inspection levels I, II and III
| Lot size | Level I | Level II | Level III |
|---|---|---|---|
| 2 to 8 | 3 (0/1) | 3 (0/1) | 3 (0/1) |
| 9 to 15 | 3 (0/1) | 3 (0/1) | 3 (0/1) |
| 16 to 25 | 3 (0/1) | 3 (0/1) | 13 (1/2) |
| 26 to 50 | 3 (0/1) | 13 (1/2) | 13 (1/2) |
| 51 to 90 | 3 (0/1) | 13 (1/2) | 20 (2/3) |
| 91 to 150 | 13 (1/2) | 20 (2/3) | 32 (3/4) |
| 151 to 280 | 13 (1/2) | 32 (3/4) | 50 (5/6) |
| 281 to 500 | 20 (2/3) | 50 (5/6) | 80 (7/8) |
| 501 to 1,200 | 32 (3/4) | 80 (7/8) | 125 (10/11) |
| 1,201 to 3,200 | 50 (5/6) | 125 (10/11) | 200 (14/15) |
| 3,201 to 10,000 | 80 (7/8) | 200 (14/15) | 315 (21/22) |
| 10,001 to 35,000 | 125 (10/11) | 315 (21/22) | 315 (21/22) |
| 35,001 to 150,000 | 200 (14/15) | 315 (21/22) | 315 (21/22) |
| 150,001 to 500,000 | 315 (21/22) | 315 (21/22) | 315 (21/22) |
| 500,001 and over | 315 (21/22) | 315 (21/22) | 315 (21/22) |
The number is the sample size. The first bracketed number is Ac: accept the lot if the number of defective units found is Ac or fewer. The second is Re: reject the lot if the number of defective units found is Re or more. The table covers single sampling plans for normal inspection only.
If the sample size equals or exceeds the lot size, inspect 100 percent. This applies to some of the small-lot cells in the table.
Some cells use a plan from another code letter. Lot 16 to 25 at level III is code letter D, but the plan used is letter E's, 13 (1/2). Lot 26 to 50 at level II is code letter D, but the plan used is letter E's, 13 (1/2). Lot 35,001 to 150,000 at level II is code letter N, but the plan used is letter M's, 315 (21/22).
From 10,001 to 35,000 upward, every level II and level III cell in this table reads 315 (21/22), as the table shows.
Where these tables come from
These tables come from MIL-STD-105E, Sampling Procedures and Tables for Inspection by Attributes (U.S. Department of Defense, 10 May 1989). ANSI/ASQ Z1.4 and ISO 2859-1 descend from it. The tables here were not compared cell by cell with the current paid editions of ANSI/ASQ Z1.4 or ISO 2859-1. Where a contract or purchase order names a standard and an edition, that one governs.
Questions people ask
What plan applies at level I for a lot in the 151 to 280 range?
The cell reads 13 (1/2): inspect 13 units, accept the lot with 1 or fewer defective units, and reject it with 2 or more. That row's code letter at level I is E, and the plan used is also letter E's.
Why does one cell show a plan from a different code letter?
The arrows in Table II-A send you to another plan when the row's own letter has no plan at that AQL. For lot 35,001 to 150,000 at level II, the code letter is N, but the plan used is letter M's, 315 (21/22).
Do levels II and III ever differ for the largest lots?
Not from 10,001 to 35,000 upward. Every level II and level III cell in that range reads 315 (21/22).
Sources
- MIL-STD-105E, Sampling Procedures and Tables for Inspection by Attributes, U.S. Department of Defense, 10 May 1989: Table I and Table II-A with its legend and footnote. Page scans: archive.org/details/MIL-STD-105E_1. Read 11 October 2026.
Checked 11 October 2026.
This page is an unofficial reference, not affiliated with any standards body, and where your contract names ANSI/ASQ Z1.4, ISO 2859-1 or another standard, use the tables of that edition.