Minimum cube sampling for any pour per IS 456:2000 Cl 15.2.2 — enter the concrete volume of each grade and get the samples,cube count and which acceptance regime applies.
The frequency is per grade — run separately for M25 columns and M30 slabs of the same pour.
IS 456:2000 Cl 15.2.2 — minimum frequency
| 1–5 m³ | 1 sample |
| 6–15 m³ | 2 samples |
| 16–30 m³ | 3 samples |
| 31–50 m³ | 4 samples |
| Above 50 m³ | 4 + 1 per 50 m³ or part |
Sampling plan
samples = cubes
The band table of IS 456:2000 Cl 15.2.2 maps concrete volume to minimum samples per grade; above 50 m³ the rule adds one sample per additional 50 m³ or part thereof. Each sample is a set of three 150 mm cubes cast from the same batch per IS 516 — so cube count is samples × 3.
The planner also flags which acceptance regime the resulting sample count triggers: fewer than four samples on a pour of 30 m³ or less means Table 11 Note 2 small-pour criteria; four or more means the standard group-of-four check (see the Cube Test Statistics calculator).
Given: raft pour of 75 m³ of M30 (run separately for any other grade in the same pour).
75 > 50 → 4 + ⌀((75 − 50)/50)⌁ = 4 + 1 = 5 samples
Cubes = 5 × 3 = 15 cubes — schedule casting across the pour, sampling randomly from intermediate discharge.
Cl 15.2.2 sets the minimum per quantity of concrete of each grade in the work — in practice evaluated per pour or per defined work section, whichever the QC plan defines. A continuous raft of 130 m³ needs 6 samples even if placed in one shift.
No — that samples the truck, not the pour. Sample randomly across the placement: different batches, different points of discharge, and never only the first or last discharge, which are unrepresentative of the bulk.
Three cubes from one sample average out specimen-to-specimen variation (compaction, curing) so the recorded strength represents the batch. The set is cast together and tested at 28 days per IS 516; individual cube deviations within a set flag handling or testing problems.
Producer control cubes verify the plant; site acceptance sampling per Cl 15.2.2 verifies the concrete as delivered and placed. Both matter and they are separate records — do not substitute one for the other in acceptance decisions.
Often used together with this calculator — pick the next step in your design or QA loop.
Deep dive: read the full significance guide — the code clauses, assumptions and site meaning behind these numbers.