BS / EN · PRELIMINARY TRIAL WORKSPACE
Explore a BS/EN trial mix: select a strength class, enter material properties and see moisture-corrected batch quantities.
01 / STRENGTH REQUIREMENT
Declared strength test age: 28 days. C30/37 means 30 MPa cylinder and 37 MPa cube characteristic strength. The pair is a class definition, not a conversion rule for individual test results.
1 m³ designed volume · measured yield still requires testing
03 / YOUR BATCH
These are illustrative trial quantities. Sand and stone use measured total moisture; mixer water accounts for aggregate absorption and water in admixture. Neither the chosen strength nor standards conformity has been demonstrated.
Prefilled numbers are demonstration assumptions. This is an absolute-volume worksheet for a BS/EN project, not a complete BRE design method or automated BS 8500 conformity check.
UNDERSTAND YOUR RESULTS
Use the UK concrete calculator to explore trial quantities for a declared cement product and measured aggregates. A BS/EN strength class describes the strength requirement; BS 8500 specification decisions also depend on the project’s exposure and other conditions.
The first number denotes characteristic cylinder strength and the second characteristic cube strength, in MPa. C25/30 therefore pairs 25 MPa cylinder with 30 MPa cube strength; C30/37 pairs 30 with 37 MPa. Keep the specimen basis and declared test age consistent when entering a required average strength or comparing test results.
Read the BS/EN references used by this worksheet →A class label does not supply a universal bucket recipe. The cement product, aggregate grading, water demand, air, workability and durability requirements affect the proportions. Changing the strength-class button above records a requirement; it does not automatically select a strength-qualified water/cement ratio.
MPA Concrete Centre: BS 8500 specification tool →Enter the project-adopted standard and edition, exposure and placing requirements, qualified water ratio, cement-product specific gravity, aggregate properties and measured moisture. Enter the sand share of aggregate absolute volume from your material evidence. This worksheet uses one declared cement product; separate-addition k-values and equivalent cement combinations are outside its calculation.
Check the method before using your quantities →The output explains trial material weights and water corrections. For ready-mixed concrete, agree the specification, quantity, consistence, placing needs and delivery arrangements with the producer. A worksheet printout alone is not a complete concrete order or a BS 8500 conformity assessment. Confirm the applicable edition during the EN 206 transition.
MPA Concrete Centre: specifying concrete in practice →A VISUAL GUIDE TO THE MIX
Start with the ingredients, then see why wet aggregate changes the batch. These concepts support every regional worksheet.
Four main ingredients, each with a different role.
Some mixes also use supplementary cementitious materials and chemical admixtures. Air occupies volume too. Their amounts depend on the specification, materials and trials.
The surface and the pores tell different stories.
Air-dry aggregate lies between oven dry and SSD. Measure absorption and total moisture; appearance alone cannot determine the correction.
Illustrative example, separate from your mix: 100 kg of oven-dry sand, 2% absorption and 5% total moisture. Both percentages use oven-dry mass.
The reference mass
100 + 2 absorbed water
100 + 5 total water
105 − 102 = 3
Batch 105 kg of wet sand to supply 102 kg on an SSD basis. Deduct 3 kg from the water otherwise added at the mixer. Account separately for moisture in other aggregates and water in liquid admixtures.
Learn more: NRMCA · aggregate moisture and ACI · batch water adjustments.
From SSD to wet batch weights: follow a complete moisture correction →
METHOD & SOURCE BOUNDARIES
Water and a qualified water/cement ratio establish cement demand. After subtracting cement, free water, admixture and air, the supplied fine-aggregate volume share divides the remaining absolute volume. Measured absorption and moisture determine the batch weights.
BS EN 206 and BS 8500 govern specification and conformity; this worksheet does not implement the full licensed BRE design tables or BS 8500 exposure, cement-performance and conformity assessments. The 2026 EN transition means the project’s governing edition must be checked. Separate additions, k-values and equivalent cement combinations are not calculated; use one declared cement product with its measured properties.
Normal-density concrete only. Special concrete, structural design and complete conformity assessment are outside this worksheet. Keep the specimen type and test age consistent. A grade change is not evidence of achieved strength.
Read the methodology and privacy details · Open this regional worksheet directly
Preliminary calculations. Not project approval or a strength prediction.
| Concrete Ratio — preliminary regional trial worksheet | ||
| Region | United Kingdom | |
| National reference context | No additional national reference selected | |
| Method | User-qualified absolute-volume trial worksheet | |
| Engine | 1.1.0 | |
| Status | Arithmetic only; strength, durability and conformity are not certified | |
| Project governing specification | Not supplied | |
| Exposure / project conditions | Not supplied | |
| Cement identity | Illustrative cement product — replace with measured properties | |
| Input / trial evidence | Not supplied; illustrative inputs | |
| Specified strength | 30 | MPa |
| Strength specimen | cylinder | |
| Declared strength test age | 28 | days |
| Required average strength · user supplied, unverified | Not supplied | MPa |
| Batch volume input | 1 | m³ |
| Total free water | 180 | kg/m³ |
| Selected water/cement ratio | 0.45 | mass / mass |
| Total air | 2 | % volume |
| Cement particle specific gravity | 3.15 | |
| Fine aggregate SSD specific gravity | 2.65 | |
| Coarse aggregate SSD specific gravity | 2.7 | |
| Sand absorption | 1 | % oven-dry mass |
| Sand total moisture | 4 | % oven-dry mass |
| Stone absorption | 1 | % oven-dry mass |
| Stone total moisture | 2 | % oven-dry mass |
| UK strength class | C30/37 | |
| Sand share of aggregate absolute volume | 38 | % |
| Admixture product dose | 0 | % cementitious mass |
| Project maximum water ratio | Not supplied | |
| Project minimum cementitious content | Not supplied | kg/m³ |
| Project maximum cementitious content | Not supplied | kg/m³ |
| Project minimum air | Not supplied | % volume |
| Material | per m³ · kg | batch · kg |
| Cement | 400 | 400 |
| Sand — as batched | 697.8574886060035 | 697.8574886060035 |
| Coarse aggregate — as batched | 1137.7833097595476 | 1137.7833097595476 |
| Water to add at mixer | 148.71475719000472 | 148.71475719000472 |
| Batch volume | 1 | m³ |
| Total batch weight | 2384.3555555555554 | kg |
| Actual water ratio | 0.45 | |
| Free water kg/m3 | 180 | |
| Mixer water kg/m3 | 148.71475719000472 | |
| Constituent | Absolute m3 per m3 | Mass kg/m3 on stated basis |
| Cement | 0.12698412698412698 | 400 |
| Sand · SSD | 0.2557460317460317 | 677.7269841269841 |
| Stone · SSD | 0.41726984126984135 | 1126.6285714285716 |
| Free water outside admixture | 0.18 | 180 |
| Air | 0.02 | 0 |
| Outstanding check | No strength or complete code conformity assessment | |
| Water and cementitious content | B = max(W / r, supplied minimum) | 180.000 / 0.450 → 400.000 kg/m³; actual W/B = 0.450. Water demand and the strength-qualified ratio are inputs, not inferred from the grade. |
| Account for paste, liquid admixture and air | Vagg = 1 − Σ(Bj / 1000 Gj) − (W − D·u)/1000 − D/(1000 GD) − air | Admixture carries 0.000 kg/m³ water. Residual aggregate absolute volume = 0.673 m³/m³. Water density reference: 1000 kg/m³. |
| Split absolute aggregate volume | FASSD = Vagg × fine volume share × 1000 GFA; CASSD = Vagg × (1 − share) × 1000 GCA | 38.000% of aggregate absolute volume goes to sand. This is not a mass percentage or a loose-bucket ratio. |
| Close the one-cubic-metre balance | VF = Vagg − CASSD / (1000 GCA); FASSD = VF × 1000 GFA | Sand 677.727 kg SSD/m³; coarse aggregate 1126.629 kg SSD/m³. The constituent absolute volumes, including air, sum to 1 m³. |
| Correct the aggregate moisture | OD = SSD / (1 + A); wet = OD × (1 + T); surface water = OD × (T − A) | Sand contributes 20.131 kg/m³ and stone 11.155 kg/m³ free surface water. Negative values represent absorption deficits. A and T are fractions of oven-dry mass in the equation. |
| Prepare the batch and test it | Mixer water = W − admixture water − sand surface water − stone surface water | 180.000 − 0.000 − 20.131 − 11.155 = 148.715 kg/m³. Multiply each ingredient by 1.000 m³. Measure workability, air, density/yield and strength; revise the trial. |
| Reference | BS EN 206-1:2026 · concrete requirements | https://landingpage.bsigroup.com/LandingPage/Undated?UPI=000000000030148156 |
| Reference | BS EN 206-2:2026 · conformity assessment | https://knowledge.bsigroup.com/products/concrete-specification-performance-production-and-conformity-conformity-assessment-and-certification |
| Reference | BS 8500-1:2023 · UK specification guidance | https://knowledge.bsigroup.com/products/concrete-complementary-british-standard-to-bs-en-206-method-of-specifying-and-guidance-for-the-specifier-1 |
| Reference | BS 8500-2:2023 · constituents and concrete | https://landingpage.bsigroup.com/LandingPage/Undated?UPI=000000000030090839 |
| Reference | MPA · BS 8500 specification tool | https://www.concretecentre.com/TCCBS8500 |
| Reference | BRE BR 331 · normal concrete mix design | https://bregroup.com/store/bookshop/design-of-normal-concrete-mixes-second-edition-br-331 |