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BS / EN · PRELIMINARY TRIAL WORKSPACE

UK concrete mix design calculator

A BS/EN project worksheet with cylinder/cube strength classes, qualified material inputs, visible absolute-volume calculations and moisture-corrected quantities.

BS EN 206-1/-2:2026 · BS 8500-1/-2:2023 · confirm the project edition

01 / STRENGTH REQUIREMENT

Choose the cylinder / cube class

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.

Total batch weight2,384.4 kg

1 m³ designed volume · measured yield still requires testing

03 / MATERIALS TO WEIGH FOR YOUR BATCH

Cement400 kg
Sand — as batched697.9 kg
Coarse aggregate — as batched1,137.8 kg
Water to add at mixer148.7 kg
Actual w/c 0.450Free water 180 kg/m³Mixer water volume 148.71 LAir 2%

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.

Use material and trial evidence to select the inputs.

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.

Water, cement and air

Total free water, including applicable aggregate surface water and admixture carrier water.

Mass ratio selected from material evidence and project requirements, not from the strength button.

Include intentionally entrained air where required. Verify the required level and actual air test.

Aggregate proportion and properties

Selected from material grading and workability evidence. This is not percentage by mass.

Absorption and total moisture below are percentages of oven-dry aggregate mass. SSD means saturated surface-dry.

Admixture solution

Use the manufacturer’s product data. Its water and full solution volume are accounted for once.

Project specification and checks

Enter a qualified target on the stated specimen basis. No IS or universal statistical margin is applied.

Blank means not supplied and not checked.

A supplied minimum increases cementitious content and reduces the actual ratio.

METHOD & SOURCE BOUNDARIES

BS/EN specification, with transparent trial arithmetic

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

Concrete Ratio · United Kingdom trial record

Preliminary calculations. Not project approval or a strength prediction.

Concrete Ratio — preliminary regional trial worksheet
RegionUnited Kingdom
National reference contextNo additional national reference selected
MethodUser-qualified absolute-volume trial worksheet
Engine1.0.0
StatusArithmetic only; strength, durability and conformity are not certified
Project governing specificationNot supplied
Exposure / project conditionsNot supplied
Cement identityIllustrative cement product — replace with measured properties
Input / trial evidenceNot supplied; illustrative inputs
Strength specimencylinder
Specified strength MPa30
UK strength classC30/37
SI input keyValue; masses kg/m3, volumes m3, strength MPa, percentages as labelled
strength30
strengthClassC30/37
specimencylinder
meanStrengthNot supplied
batch1
water180
ratio0.45
air2
cementSG3.15
faSG2.65
caSG2.7
coarseBulk0.62
dryRoddedDensity1600
fineVolumeShare38
flyAsh0
slag0
flyAshSG2.2
slagSG2.9
dose0
admixtureSG1.1
admixtureWater0
faAbsorption1
caAbsorption1
faMoisture4
caMoisture2
maxRatioNot supplied
minBinderNot supplied
maxBinderNot supplied
minAirNot supplied
Materialper m³ · kgbatch · kg
Cement400400
Sand — as batched697.8574886060035697.8574886060035
Coarse aggregate — as batched1137.78330975954761137.7833097595476
Water to add at mixer148.71475719000472148.71475719000472
Batch volume1m³
Total batch weight2384.3555555555554kg
Actual water ratio0.45
Free water kg/m3180
Mixer water kg/m3148.71475719000472
ConstituentAbsolute m3 per m3Mass kg/m3 on stated basis
Cement0.12698412698412698400
Sand · SSD0.2557460317460317677.7269841269841
Stone · SSD0.417269841269841351126.6285714285716
Free water outside admixture0.18180
Air0.020
Outstanding checkNo strength or complete code conformity assessment
Water and cementitious contentB = 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 airVagg = 1 − Σ(Bj / 1000 Gj) − (W − D·u)/1000 − D/(1000 GD) − airAdmixture carries 0.000 kg/m³ water. Residual aggregate absolute volume = 0.673 m³/m³. Water density reference: 1000 kg/m³.
Split absolute aggregate volumeFASSD = Vagg × fine volume share × 1000 GFA; CASSD = Vagg × (1 − share) × 1000 GCA38.000% of aggregate absolute volume goes to sand. This is not a mass percentage or a loose-bucket ratio.
Close the one-cubic-metre balanceVF = Vagg − CASSD / (1000 GCA); FASSD = VF × 1000 GFASand 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 moistureOD = 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 itMixer water = W − admixture water − sand surface water − stone surface water180.000 − 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.
ReferenceBS EN 206-1:2026 · concrete requirementshttps://landingpage.bsigroup.com/LandingPage/Undated?UPI=000000000030148156
ReferenceBS EN 206-2:2026 · conformity assessmenthttps://knowledge.bsigroup.com/products/concrete-specification-performance-production-and-conformity-conformity-assessment-and-certification
ReferenceBS 8500-1:2023 · UK specification guidancehttps://knowledge.bsigroup.com/products/concrete-complementary-british-standard-to-bs-en-206-method-of-specifying-and-guidance-for-the-specifier-1
ReferenceBS 8500-2:2023 · constituents and concretehttps://landingpage.bsigroup.com/LandingPage/Undated?UPI=000000000030090839
ReferenceMPA · BS 8500 specification toolhttps://www.concretecentre.com/TCCBS8500
ReferenceBRE BR 331 · normal concrete mix designhttps://bregroup.com/store/bookshop/design-of-normal-concrete-mixes-second-edition-br-331