Concrete Mix Calculator

How the Concrete Mix Ratio Calculator Works

Choose the finished volume and a ratio expressed as binder, sand, and stone. The tool first allows extra dry volume because dry ingredients settle into fewer finished cubic feet after water and mixing. It then divides that dry allowance by the selected ratio. The result is a planning estimate for material takeoff, not a mix design or a strength specification.

Choosing a Mix Ratio

A 1 : 2 : 3 mix divides the dry material into six parts: one binder part, two sand parts, and three stone parts. The 1 : 1.5 : 3 option has a higher binder proportion. Actual materials vary by moisture, grading, local supply, and batch method. Follow the product instructions or a project-specific specification when strength, exposure, or structural performance matters.

Concrete Mix Calculation Formula

Begin with the finished wet volume needed for the project. The calculator multiplies that amount by a 1.54 dry-volume factor to allow for voids and settlement in the separate ingredients. For a 1 : 2 : 3 ratio, add the parts to get six. Binder equals dry volume × 1/6, sand equals dry volume × 2/6, and stone equals dry volume × 3/6. A finished cubic yard is 27 cubic feet, so the planning dry volume is 41.58 cubic feet. The three estimated portions are about 6.93 cubic feet of binder, 13.86 cubic feet of sand, and 20.79 cubic feet of stone before expressing them in purchase units.

Binder bags are rounded up because partial bags are not normally purchased. Sand and stone remain volume estimates and may be changed between cubic feet and cubic yards. Bulk aggregate is often sold by weight, but weight depends on material density and moisture. Ask the supplier for the correct volume-to-weight factor for the specific product instead of relying on one universal tons-per-yard value.

Worked Small-Batch Example

Suppose a repair needs 10 cubic feet of finished concrete and the selected ratio is 1 : 2 : 3. Applying the 1.54 factor gives 15.4 cubic feet of dry ingredients. Dividing by six gives about 2.57 cubic feet of binder, 5.13 cubic feet of sand, and 7.70 cubic feet of stone. The calculator converts binder volume to an estimated whole-bag count using its planning assumption and lets you enter prices for binder bags and aggregate. The quick cost is material only. It excludes water, admixtures, pigments, delivery, mixing equipment, labor, waste, and testing.

For very small jobs, compare this takeoff with packaged concrete using the Concrete Bag Calculator. Premixed bags use manufacturer-controlled proportions and publish a yield per bag. For larger or performance-critical placements, ready-mixed concrete or an approved project mix may be more practical than batching separate ingredients on site.

Mixing and Measurement Considerations

Use one consistent container or calibrated batch box for every ratio part; switching between shovels, buckets, and guessed piles introduces large errors. Keep aggregates reasonably consistent and account for wet sand, which occupies a different apparent volume and contributes water. Add water according to the applicable product or mix instructions. Extra water may make placement easier but can reduce quality and increase shrinkage. Mix each batch uniformly, place it within the allowed time, consolidate as required, and follow the curing plan.

The displayed ratios are convenient takeoff options, not proof of compressive strength, durability, air content, slump, or suitability for freezing, sulfate exposure, reinforcement, or structural loads. When those properties matter, use a specified mix and qualified guidance. The calculator estimates how a chosen ratio divides volume; it does not select that ratio for the project.