About Concrete Mix Design Calculator
The concrete mix design calculator proportions a normal-weight structural concrete mix using the ACI 211.1 standard practice. It is used by concrete technologists and engineers to derive the water/cement ratio, the cement, water, and aggregate quantities, and a trial batch from a target strength, slump, and aggregate size.
Choose the target 28-day strength, exposure class, maximum aggregate size, slump, and any fly ash or slag replacement. The tool returns the w/c ratio, water and cement content, fine and coarse aggregate masses, a yield check, total density, and a scaled trial batch that update as you adjust the inputs.
How It Works
- Look up the water/cement ratio for the target strength and read the mixing water from the slump and maximum aggregate size table.
- Compute the total cementitious content as water divided by the w/c ratio, then apply any fly ash or slag replacement to the Portland cement.
- Use the absolute volume method to fill one cubic metre: add the air, water, cement, SCM, and coarse aggregate volumes and assign the remainder to fine aggregate.
- Convert volumes to masses with material densities, run a yield check toward 1.0 m3, report total density, and scale every quantity to a 0.03 m3 trial batch.
Worked Example
For 30 MPa non-air-entrained concrete at 75-100 mm slump with 20 mm aggregate, the w/c ratio is 0.50 and the mixing water is 193 kg/m3, so the cement content is 193 / 0.50 = 386 kg/m3. With 0.66 m3 of coarse aggregate at 2700 kg/m3 (1782 kg/m3) and fine aggregate filling the residual volume, the mix reaches a total density near 2373 kg/m3.
Formulas
- Cement content
cement = water / wc_ratio- SCM replacement
adjusted_cement = total_cementitious - flyAsh - slag- Fine aggregate by absolute volume
fineVol = 1.0 - airVol - waterVol - cementVol - scmVol - coarseVol- Aggregate mass from volume
mass = volume * density
Standards & References
- ACI 211.1
- EN 206
- AS 1379
Frequently Asked Questions
Which mix design method does this calculator use?
It implements the ACI 211.1 Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete, using its w/c ratio, water content, and absolute volume tables. EN 206 and AS 1379 are listed for context.
How does the water/cement ratio relate to strength?
A lower w/c ratio gives higher strength, so the tool interpolates the required ratio from the ACI strength tables for your target 28-day strength, returning no result if the target falls outside the tabulated range.
Can I replace cement with fly ash or slag?
Yes. Enter a fly ash percentage (up to 40%) and a slag percentage (up to 70%) of the cementitious content; the tool deducts these from the Portland cement and accounts for their lower densities in the volume balance.
What is the yield check for?
The yield check sums the absolute volumes of all ingredients and should equal about 1.0 m3. A value within 0.02 of 1.0 confirms the proportions are internally consistent before you scale to a trial batch.