Concrete Mix Calculator (Cement, Sand and Gravel)
This concrete mix calculator splits the volume of concrete you need into cement, sand and gravel for a mix ratio you choose.
A 10 × 10 ft slab 4 inches thick is 33.3 cubic feet of concrete (1.23 yd³). A 1:2:3 mix with a 1.54 dry-volume factor needs about 8.6 cubic feet of cement (9 bags of 94 lb), 17.1 cubic feet of sand and 25.7 cubic feet of gravel.
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How a concrete mix ratio works
A mix ratio such as 1:2:3 means one part cement, two parts sand and three parts gravel (coarse aggregate), measured by volume. Water is added separately. To find how much of each you need, start with the volume of concrete, convert it to dry volume, then split it by the ratio.
dry volume = concrete volume × 1.54
each material = dry volume × its parts ÷ total parts
Example: a 10 × 10 ft slab 4 in thick is 100 × 0.333 = 33.3 cu ft (1.23 yd³). Dry volume is 33.3 × 1.54 = 51.3 cu ft. For 1:2:3 the parts total 6: cement 51.3 ÷ 6 = 8.6 cu ft, sand 17.1 cu ft and gravel 25.7 cu ft. A 94 lb bag of cement is about 1 cu ft, so plan 9 bags.
Common mix ratios
| Ratio | Typical use | Cement for 1 yd³ (cu ft) |
|---|---|---|
| 1:2:3 | General slabs, walks, patios | 6.9 |
| 1:1.5:3 | Footings and stronger work | 7.6 |
| 1:2:4 | Lean fill, bases | 5.9 |
For structural or load-bearing work, a ready-mix supplier or engineer should specify the mix by strength, not by a rule-of-thumb ratio. State transportation departments publish mix proportions by strength class, with water-cement ratio as the key control on durability.
Tips
- Too much water weakens concrete; add only enough for workability.
- Bagged mixes such as 60 lb or 80 lb pre-mix save you the blending; use the concrete calculator to count bags.
- For big pours, compare mixing yourself with ready-mix in the concrete cost calculator.
- Convert sand and gravel yards to tons with the yards to tons calculator.
Frequently asked questions
What is the ratio for a concrete mix?
A common general-purpose mix is 1 part cement, 2 parts sand and 3 parts gravel by volume, with enough water to be workable. Stronger or leaner mixes change those parts.
How much cement, sand and gravel for 1 cubic yard of concrete?
With a 1:2:3 mix and a 1.54 dry factor you need about 6.9 cu ft of cement (7 bags), 13.9 cu ft of sand and 20.8 cu ft of gravel.
Why is the dry volume bigger than the concrete volume?
Dry materials have air gaps that close up when water is added, so you need roughly 1.5 times the finished volume in dry material.
How many bags of cement are in a cubic yard of concrete?
About 6 to 7 bags of 94 lb cement for a 1:2:3 mix, depending on the factor used. Check your supplier's mix design.
Can I use this for structural concrete?
No. Structural work should follow an engineered mix design or ready-mix supplier specification.
Sources and further reading
- Portland cement concrete proportions (mix design guidance) — Iowa Department of Transportation
- NIST Special Publication 811: conversion factors — National Institute of Standards and Technology
These references support the general guidance on this page. The calculator applies the standard formulas shown above to the numbers you enter.
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Related calculators
. Estimates only. Always confirm quantities with your supplier or a qualified contractor before ordering, and add extra for waste and site conditions.