AQL sampling calculator (ISO 2859-1 / ANSI/ASQ Z1.4)
For a lot of 3,200 units at general inspection level II and AQL 2.5, the standard tables give code letter K: inspect 125 units, accept the lot with 7 or fewer defectives, reject it at 8. The tables below are single sampling plans for normal inspection, levels I, II and III, for AQL 0.65 to 6.5.
Worked example
Lot of 3,200 units, general inspection level II, AQL 2.5, single sampling, normal inspection.
- Table I: 3,200 falls in the 1,201 to 3,200 row, so level II gives code letter K.
- Table II-A: letter K has a sample size of 125.
- Under AQL 2.5: Ac 7, Re 8. Accept with 7 or fewer defectives; reject at 8 or more.
One unit more changes the answer: a lot of 3,201 moves to letter L, a sample of 200, and Ac 10 / Re 11 at AQL 2.5.
Level II: lot size to sample size, with accept and reject numbers
General inspection level II, normal inspection, single sampling. Where an arrow moves the plan to another row, the sample size shown under the AQL is the one to use. If that sample is as large as the lot or larger, inspect the whole lot.
| Lot size | Code letter | Sample size | AQL 0.65 | AQL 1.0 | AQL 1.5 | AQL 2.5 | AQL 4.0 | AQL 6.5 |
|---|---|---|---|---|---|---|---|---|
| 2 to 8 | A | 2 | Ac 0 / Re 1, sample 20 | Ac 0 / Re 1, sample 13 | Ac 0 / Re 1, sample 8 | Ac 0 / Re 1, sample 5 | Ac 0 / Re 1, sample 3 | Ac 0 / Re 1 |
| 9 to 15 | B | 3 | Ac 0 / Re 1, sample 20 | Ac 0 / Re 1, sample 13 | Ac 0 / Re 1, sample 8 | Ac 0 / Re 1, sample 5 | Ac 0 / Re 1 | Ac 0 / Re 1, sample 2 |
| 16 to 25 | C | 5 | Ac 0 / Re 1, sample 20 | Ac 0 / Re 1, sample 13 | Ac 0 / Re 1, sample 8 | Ac 0 / Re 1 | Ac 0 / Re 1, sample 3 | Ac 1 / Re 2, sample 8 |
| 26 to 50 | D | 8 | Ac 0 / Re 1, sample 20 | Ac 0 / Re 1, sample 13 | Ac 0 / Re 1 | Ac 0 / Re 1, sample 5 | Ac 1 / Re 2, sample 13 | Ac 1 / Re 2 |
| 51 to 90 | E | 13 | Ac 0 / Re 1, sample 20 | Ac 0 / Re 1 | Ac 0 / Re 1, sample 8 | Ac 1 / Re 2, sample 20 | Ac 1 / Re 2 | Ac 2 / Re 3 |
| 91 to 150 | F | 20 | Ac 0 / Re 1 | Ac 0 / Re 1, sample 13 | Ac 1 / Re 2, sample 32 | Ac 1 / Re 2 | Ac 2 / Re 3 | Ac 3 / Re 4 |
| 151 to 280 | G | 32 | Ac 0 / Re 1, sample 20 | Ac 1 / Re 2, sample 50 | Ac 1 / Re 2 | Ac 2 / Re 3 | Ac 3 / Re 4 | Ac 5 / Re 6 |
| 281 to 500 | H | 50 | Ac 1 / Re 2, sample 80 | Ac 1 / Re 2 | Ac 2 / Re 3 | Ac 3 / Re 4 | Ac 5 / Re 6 | Ac 7 / Re 8 |
| 501 to 1,200 | J | 80 | Ac 1 / Re 2 | Ac 2 / Re 3 | Ac 3 / Re 4 | Ac 5 / Re 6 | Ac 7 / Re 8 | Ac 10 / Re 11 |
| 1,201 to 3,200 | K | 125 | Ac 2 / Re 3 | Ac 3 / Re 4 | Ac 5 / Re 6 | Ac 7 / Re 8 | Ac 10 / Re 11 | Ac 14 / Re 15 |
| 3,201 to 10,000 | L | 200 | Ac 3 / Re 4 | Ac 5 / Re 6 | Ac 7 / Re 8 | Ac 10 / Re 11 | Ac 14 / Re 15 | Ac 21 / Re 22 |
| 10,001 to 35,000 | M | 315 | Ac 5 / Re 6 | Ac 7 / Re 8 | Ac 10 / Re 11 | Ac 14 / Re 15 | Ac 21 / Re 22 | Ac 21 / Re 22, sample 200 |
| 35,001 to 150,000 | N | 500 | Ac 7 / Re 8 | Ac 10 / Re 11 | Ac 14 / Re 15 | Ac 21 / Re 22 | Ac 21 / Re 22, sample 315 | Ac 21 / Re 22, sample 200 |
| 150,001 to 500,000 | P | 800 | Ac 10 / Re 11 | Ac 14 / Re 15 | Ac 21 / Re 22 | Ac 21 / Re 22, sample 500 | Ac 21 / Re 22, sample 315 | Ac 21 / Re 22, sample 200 |
| 500,001 and over | Q | 1,250 | Ac 14 / Re 15 | Ac 21 / Re 22 | Ac 21 / Re 22, sample 800 | Ac 21 / Re 22, sample 500 | Ac 21 / Re 22, sample 315 | Ac 21 / Re 22, sample 200 |
How to read the AQL tables
- Find the lot size in Table I and read the sample size code letter under the inspection level. Level II is the default; level I takes smaller samples and level III larger ones.
- Find the code letter in Table II-A: it gives the sample size, and under your AQL the acceptance number (Ac) and rejection number (Re).
- If the cell holds an arrow, use the first plan below a down arrow or above an up arrow. The sample size changes to the one on that plan's row.
- Inspect the sample. If the number of defectives is at or below Ac, accept the lot; at or above Re, reject it.
- If the sample size equals or exceeds the lot size, inspect 100% of the lot.
Table I: sample size code letters (general inspection levels)
| Lot size | Level I | Level II | Level III |
|---|---|---|---|
| 2 to 8 | A | A | B |
| 9 to 15 | A | B | C |
| 16 to 25 | B | C | D |
| 26 to 50 | C | D | E |
| 51 to 90 | C | E | F |
| 91 to 150 | D | F | G |
| 151 to 280 | E | G | H |
| 281 to 500 | F | H | J |
| 501 to 1,200 | G | J | K |
| 1,201 to 3,200 | H | K | L |
| 3,201 to 10,000 | J | L | M |
| 10,001 to 35,000 | K | M | N |
| 35,001 to 150,000 | L | N | P |
| 150,001 to 500,000 | M | P | Q |
| 500,001 and over | N | Q | R |
Table II-A: single sampling plans for normal inspection
Ac = acceptance number, Re = rejection number. ↓ = use the first sampling plan below the arrow; if the sample size equals or exceeds the lot size, inspect 100%. ↑ = use the first sampling plan above the arrow.
| Code letter | Sample size | AQL 0.65 (Ac / Re) | AQL 1.0 (Ac / Re) | AQL 1.5 (Ac / Re) | AQL 2.5 (Ac / Re) | AQL 4.0 (Ac / Re) | AQL 6.5 (Ac / Re) |
|---|---|---|---|---|---|---|---|
| A | 2 | ↓ | ↓ | ↓ | ↓ | ↓ | 0 / 1 |
| B | 3 | ↓ | ↓ | ↓ | ↓ | 0 / 1 | ↑ |
| C | 5 | ↓ | ↓ | ↓ | 0 / 1 | ↑ | ↓ |
| D | 8 | ↓ | ↓ | 0 / 1 | ↑ | ↓ | 1 / 2 |
| E | 13 | ↓ | 0 / 1 | ↑ | ↓ | 1 / 2 | 2 / 3 |
| F | 20 | 0 / 1 | ↑ | ↓ | 1 / 2 | 2 / 3 | 3 / 4 |
| G | 32 | ↑ | ↓ | 1 / 2 | 2 / 3 | 3 / 4 | 5 / 6 |
| H | 50 | ↓ | 1 / 2 | 2 / 3 | 3 / 4 | 5 / 6 | 7 / 8 |
| J | 80 | 1 / 2 | 2 / 3 | 3 / 4 | 5 / 6 | 7 / 8 | 10 / 11 |
| K | 125 | 2 / 3 | 3 / 4 | 5 / 6 | 7 / 8 | 10 / 11 | 14 / 15 |
| L | 200 | 3 / 4 | 5 / 6 | 7 / 8 | 10 / 11 | 14 / 15 | 21 / 22 |
| M | 315 | 5 / 6 | 7 / 8 | 10 / 11 | 14 / 15 | 21 / 22 | ↑ |
| N | 500 | 7 / 8 | 10 / 11 | 14 / 15 | 21 / 22 | ↑ | ↑ |
| P | 800 | 10 / 11 | 14 / 15 | 21 / 22 | ↑ | ↑ | ↑ |
| Q | 1,250 | 14 / 15 | 21 / 22 | ↑ | ↑ | ↑ | ↑ |
| R | 2,000 | 21 / 22 | ↑ | ↑ | ↑ | ↑ | ↑ |
Sources
Checked on 27 September 2026
ISO 2859-1 and ANSI/ASQ Z1.4 are sold by ISO and ASQ. Their Table I and Table II-A share the values of MIL-STD-105E, the US Department of Defense standard they derive from; the values here were checked against MIL-STD-105E and against IS 2500 (Part 1):2000, the Bureau of Indian Standards' identical adoption of ISO 2859-1:1999.
Single sampling, normal inspection only. Tightened and reduced inspection, switching rules and double or multiple sampling use other tables in the same standards.
Questions about this tool
What is the AQL sample size for a lot of 3,200?
At general inspection level II, a lot of 3,200 is code letter K, a sample of 125 units. At AQL 2.5 the lot is accepted with 7 or fewer defectives and rejected at 8. A lot of 3,201 moves to letter L and 200 units.
What do the arrows in the AQL table mean?
A down arrow means use the first sampling plan below it, an up arrow the first plan above it. The sample size then changes to the one on that plan's row, which can be larger or smaller than the code letter's own sample size.
Which inspection level should I use?
Level II is the standard's default and the usual choice. Level I takes a smaller sample where less discrimination is needed; level III a larger one for greater discrimination.
What AQL is normally used for critical, major and minor defects?
A common choice for consumer goods is zero tolerance for critical defects, AQL 2.5 for major and AQL 4.0 for minor. It is common practice, not part of the standard; the contract sets the AQL.
Is ANSI/ASQ Z1.4 the same as ISO 2859-1?
For single sampling under normal inspection, the code letters, sample sizes and accept and reject numbers are the same. Both come from MIL-STD-105E.
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