AQL Calculator
Look up the AQL sampling plan for your lot: code letter, sample size and accept / reject numbers per ANSI/ASQ Z1.4 and ISO 2859-1.
An AQL sampling plan tells you, before an inspection starts, exactly how many units to pull from a lot and how many defects you can find before the lot fails. This calculator does the table work for you: give it the lot size, the inspection level and the AQL (acceptable quality limit), and it returns the sample size code letter, the sample size n, and the accept (Ac) and reject (Re) numbers from Table I and Table II-A of ANSI/ASQ Z1.4 — the same tables published as ISO 2859-1 and, historically, MIL-STD-105E.
Enter the lot size, choose an inspection level, then set an AQL for each defect class — or tap one of the common combinations — and the plan appears below: code letter, one shared sample size, and the accept / reject numbers for every class, with the table arrows already followed.
Common industry combinations — adjust freely to your purchase order.
The four preset buttons cover the combinations most purchase orders actually use:
- General merchandise (0 / 2.5 / 4.0) — the set most inspection services suggest by default for ordinary consumer goods: zero tolerance on critical defects, a balanced line for everything else.
- Stricter major (0 / 1.5 / 4.0) — tightens the major line one step and leaves minor defects on the general setting — a common pick for clothing and household goods, where the product itself has to be right but small cosmetic slips are not worth failing a lot over.
- High quality (0 / 1.0 / 2.5) — the combination behind most branded goods and electronics orders, where workmanship and finish both get checked hard.
- Lenient (0 / 4.0 / 6.5) — fits low-value and promotional goods, where the cost of inspecting has to stay in proportion to the price of the item.
In all four, critical stays at 0: one critical defect in the sample is enough to fail the lot. Treat the presets as a starting point and adjust the three numbers freely — the figures on your purchase order always win.
Start with General II and the General merchandise combination (0 / 2.5 / 4.0). That pairing is the default most purchase orders fall back on, and it fits the great majority of ordinary consumer goods.
It also helps to know what actually lands in each class:
- Critical — a safety or legal risk: a sharp edge on a kitchen tool, a small part that can pull off a children's toy, an electrical fault. These sit at AQL 0 — one in the sample fails the lot.
- Major — the product doesn't work or look the way it should, and a buyer would send it back: a function that fails, an obvious colour mismatch, a crack or a break.
- Minor — small slips you only notice up close: a loose thread end, a tiny mark, a slight print offset.
Tighten up when the goods carry your brand name, are headed for the gift market, or are electronics — pick High quality, or Stricter major if only the major line needs to be tougher. Loosen to Lenient for low-value promotional goods, where strict lines would be out of proportion to what the items sell for.
And if your purchase order or contract already names an inspection level and AQL numbers, those always win — set the tool to match them exactly.
Source: ANSI/ASQ Z1.4 / ISO 2859-1, Table I and Table II-A — single sampling plans, normal inspection. Last verified: November 2026.
How to use
- Enter the lot size — the total number of units in the batch being inspected.
- Pick the inspection level. General Level II is the default in most purchase contracts; Level I inspects less, Level III inspects more.
- Set an AQL for each defect class — critical, major, minor — or tap one of the common-combination presets under the result and adjust from there.
- Read the plan and the summary table: inspect n units, count each defect class separately, and compare each class count with its own Ac (accept at or below) and Re (reject at or above).
About this tool
The part people get wrong by hand is the arrows. Some cells of Table II-A contain no plan at all, just an arrow: down means use the first plan below, up means the first plan above — with that plan’s sample size, not the one on your row. This calculator follows the arrows and tells you when it did, so the sample size you read is the sample size you actually inspect. If the plan it lands on asks for a sample as large as the lot itself, the standard’s answer is simple: inspect 100% of the lot.
AQL numbers are not percentages of defects you “may ship”. The AQL is the worst process average that is still considered acceptable as a series average, and the tables are built so lots at that quality level pass most of the time. Buyers usually set different AQLs per defect class — a common consumer-goods setup is 0 for critical defects, 2.5 for major and 4.0 for minor — and the summary table under the result reads all three classes in one pass — one shared sample, one Ac/Re pair per class.
Everything runs in your browser. Your lot sizes and inspection settings are never uploaded, sent to a server or stored.
How it works
Step 1 — Table I: the lot size and inspection level give a sample size code letter (A to R). Step 2 — Table II-A: the code letter fixes the sample size n (A = 2, B = 3, C = 5, D = 8, E = 13, F = 20, G = 32, H = 50, J = 80, K = 125, L = 200, M = 315, N = 500, P = 800, Q = 1,250, R = 2,000), and the AQL column gives the acceptance number Ac and rejection number Re for that plan.
Arrow rule: a ↓ in the cell means use the first sampling plan below the arrow in that column; a ↑ means the first plan above. The sample size of the plan you land on replaces your row’s sample size. If the resulting sample size equals or exceeds the lot size, inspect the entire lot instead.
Several defect classes share one sample: if the classes’ AQLs point to different sample sizes (an arrow can do that), the largest sample size is used for every class, and each class reads its Ac/Re from that sample size’s row in its own AQL column. A class set to AQL 0 is not read from the table at all — it accepts only on zero defects (Ac 0, Re 1) at the shared sample size.
Worked examples
Lot of 2,500, Level II, AQL 1.0: Table I gives code letter K (sample size 125). In Table II-A, row K at AQL 1.0 reads Ac 3 / Re 4: inspect 125 units, accept with 3 or fewer defects, reject at 4.
Lot of 5,000, Level II, AQL 2.5 and 4.0: Code letter L, sample size 200. AQL 2.5 (a typical major-defect level) reads Ac 10 / Re 11; AQL 4.0 (typical minor level) reads Ac 14 / Re 15 — both read from the same 200-unit sample.
When the arrow moves you: lot of 100, Level II, AQL 0.25: Table I gives code letter F, but row F at AQL 0.25 holds a down arrow — and so does row G below it. The first plan below the arrows is row H: sample size 50, Ac 0 / Re 1. The calculator follows the arrow and uses H’s sample size, not F’s 20.
Frequently asked questions
What is an AQL sampling plan?
It is a rule, fixed before inspection, that pairs a sample size with two numbers: Ac (accept the lot at or below this many defects in the sample) and Re (reject at or above this many). AQL plans come from ANSI/ASQ Z1.4 / ISO 2859-1 and are how most factory and pre-shipment inspections decide pass or fail without checking every unit.
Which inspection level should I use?
General Level II unless your contract says otherwise — it is the standard default. Level I uses a smaller sample and discriminates less, suited to cheap or low-risk checks; Level III uses a larger sample and discriminates more, suited to high-value or problem-prone products. The special levels S-1 to S-4 (for destructive or expensive tests) are not covered by this calculator.
What do the arrows in the AQL table mean?
Some Table II-A cells hold an arrow instead of a plan. Down means take the first plan below in that AQL column; up means the first plan above — always with that plan’s sample size. This calculator follows arrows automatically and flags when the plan shown came from a different row than your code letter.
Is AQL 2.5 the same as allowing 2.5% defects?
No. The AQL is the process average quality level the plan is designed to accept most of the time, not a licence to ship 2.5% defective units. A lot can fail an AQL 2.5 plan with a defect rate below 2.5% in the sample if the count reaches Re, and defective units found in the sample are still removed or reworked.
Can I use one sample for critical, major and minor defects?
Yes — that is the normal practice. You draw one sample of size n, sort every defect found into its class, and compare each class count against its own Ac/Re from its own AQL column. The lot fails if any class reaches its Re. The summary table under the result shows all three classes at once — set the three AQLs above and read each class’s pair from its own row.
Does this replace the standard?
No. This is a simplified lookup of Tables I and II-A for single sampling plans under normal inspection, covering AQL 0.065 to 6.5. Tightened and reduced inspection, double and multiple sampling plans, and switching rules live in the full standard — for contractual disputes, the purchased standard (ANSI/ASQ Z1.4 or ISO 2859-1) is the authority.
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