Work out a complete concrete mix design in five steps. Enter the specified strength, exposure class, target slump and your aggregate test data, and the calculator returns the water/cementitious ratio, the quantity of cement, water, coarse and fine aggregate per unit volume, and moisture-corrected batch weights for the volume you are actually pouring — including how many cement bags to order.
Proportions follow the ACI 211.1 absolute-volume method, with the water/cementitious ratio taken as the lower of the strength requirement and the durability limit for your exposure class. Switch between metric (SI) and imperial units at the top of the form; every result converts with it.
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Trial batches are required. Adjust water and admixture dosage on site to reach the specified slump without exceeding the water/cement ratio.
How the calculation works
- Required average strength. Your specified f’c is raised to a target mean strength f’cr. If you enter a known standard deviation from at least 30 test results, the ACI 318 statistical margin is used; leave it at zero and the ACI 301 no-data margin applies instead.
- Water/cementitious ratio. Interpolated from the ACI 211.1 strength table, then capped by the durability limit for the exposure class you pick. The results panel tells you which of the two governed.
- Water and air content. Read from the ACI 211.1 tables by nominal maximum aggregate size and target slump, interpolated in both directions. Air-entrained mixes use the air-entrained table and the recommended air content for the exposure severity.
- Cementitious content. Water divided by the water/cementitious ratio, with an optional minimum binder content and an optional fly ash or slag replacement percentage.
- Coarse aggregate. Bulk volume factor interpolated from the ACI table by aggregate size and the fineness modulus of your sand, multiplied by the dry-rodded unit weight.
- Fine aggregate by absolute volume. Whatever volume is left once water, cement, SCM, coarse aggregate and air are accounted for. The Checks section confirms the volumes total exactly 1.000 m³.
- Moisture correction. Aggregate absorption and site moisture content are used to convert saturated-surface-dry design weights into as-is batch weights, with the free water deducted from the mixing water.
- Batch quantities. Everything scaled to your pour volume, with water in litres or gallons and cement rounded up to whole bags.
What to have ready
- Specified compressive strength, and the standard deviation of your recent cylinder results if you have it
- Exposure class — freeze-thaw, sulfate, watertightness or chloride exposure
- Target slump and the nominal maximum aggregate size
- Fineness modulus of the fine aggregate, from the sieve analysis
- Bulk specific gravity (SSD) of cement, coarse and fine aggregate
- Dry-rodded unit weight of the coarse aggregate
- Absorption for both aggregates, and moisture content measured on the day of the pour
Sensible defaults are filled in for all of them, so you can get a feel for the output before your test data arrives.
Notes and limitations
This is a design starting point, not a substitute for trial batches. ACI 211.1 assumes normal-weight aggregate and conventional mixes; the tables do not cover self-consolidating concrete, high-range water reducers beyond the reduction percentage you enter, lightweight aggregate, or fibre-reinforced mixes. Air content, slump and strength must all be confirmed on trial batches, and water or admixture dosage adjusted on site to hit the specified slump without exceeding the water/cementitious ratio the calculator gives you.
Exposure class limits follow ACI 318 Table 19.3.2.1 in simplified form. Where your project specification is stricter than the code minimum, enter the specification’s own water/cementitious ratio in the override field on step 3 and it will be used as-is.
You can print the finished mix design or save it as a PDF from the results panel, and email a copy to yourself for the site file.
ACI 211.1 Concrete Mix Design Reference Tables
The tables below summarise the ACI 211.1 water-cement ratio limits and cement content ranges for normal-weight, non-air-entrained concrete cured 28 days in a moist environment. These values are starting points; final proportions must account for aggregate type, admixtures, and exposure class.
Water-Cement Ratio vs. Compressive Strength
| Target f’c (psi) | Target f’c (MPa) | Max w/c Ratio | Min Cement (lb/yd³) | Typical Application |
|---|---|---|---|---|
| 2,500 | 17.2 | 0.67 | 470 | Footings, mass fill, unreinforced slabs |
| 3,000 | 20.7 | 0.58 | 520 | Residential slabs, sidewalks, driveways |
| 3,500 | 24.1 | 0.51 | 560 | Structural slabs, beams, moderate exposure |
| 4,000 | 27.6 | 0.44 | 610 | Columns, high-load beams, parking decks |
| 5,000 | 34.5 | 0.40 | 660 | High-performance concrete, bridges |
| 6,000 | 41.4 | 0.32 | 720 | Pre-stressed concrete, marine structures |
Source: ACI 211.1, Table 6.3.4(a). Non-air-entrained concrete, 28-day moist cure. Values are maximums for w/c and minimums for cement; use the stricter requirement where multiple constraints apply.
Slump vs. Concrete Workability
| Slump (in) | Workability Class | Typical Application |
|---|---|---|
| 1–2 | Stiff | Pavements, mass concrete, vibrated road slabs |
| 3–4 | Medium | Beams, columns, walls, normal slabs (most common) |
| 5–6 | Fluid | Heavily reinforced sections, pumped concrete |
| > 6 | Very Fluid / SCC | Self-consolidating concrete (requires superplasticiser) |
Concrete Mix Design Calculator FAQ
What is the water-cement ratio for 3,000 psi concrete?
ACI 211.1 specifies a maximum w/c ratio of 0.58 for non-air-entrained concrete targeting 3,000 psi (20.7 MPa) at 28 days. Using more water weakens the cement paste and increases permeability; using less improves strength and durability but reduces workability. For concrete exposed to deicers or freezing, ACI 318 caps w/c at 0.45 regardless of strength.
How much cement is needed per cubic yard of 4,000 psi concrete?
Approximately 610 lb of cement per cubic yard (≈ 6 standard 94-lb bags) for non-air-entrained 4,000 psi concrete per ACI 211.1. This assumes typical coarse aggregate and no supplementary cementitious materials. When fly ash or slag replaces a portion of cement, total binder content stays similar but Portland cement content drops proportionally.
What does ACI 211.1 cover?
ACI 211.1 “Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete” is the primary American guideline for proportioning concrete mixes by absolute volume. The six-step method selects: (1) slump, (2) maximum aggregate size, (3) mixing water, (4) w/c ratio, (5) cement content, and (6) aggregate volumes. The 211.2 companion covers structural lightweight concrete.
How does air entrainment affect concrete mix design?
Entrained air requires 10–15% less mixing water for the same slump, which partially offsets the strength penalty from the air voids. As a rule of thumb, each 1% of entrained air reduces 28-day compressive strength by about 5% at a constant w/c ratio. For freeze-thaw resistance, ASTM C260 air-entraining admixtures target 4–7% total air content depending on aggregate size.
What is the standard 28-day compressive strength test?
ASTM C39 “Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens” governs the test. Standard cylinders are 6 × 12 in or 4 × 8 in, moist-cured for 28 days, then loaded to failure in a compression machine. The result is reported as f’c. Most projects also cast 7-day cylinders to verify early-strength gain before post-tensioning, form stripping, or loading.