Concrete Mix Ratio Calculator
Short answer: 1 cubic yard of M15 concrete (1:2:4) needs about 6 bags of cement, 11.88 cu ft of sand and 23.76 cu ft of aggregate before waste. Enter your volume and mix below.
Calculate your mix
How the calculation works
Dry volume = wet volume × 1.54. Dry ingredients occupy more space than wet concrete because sand and aggregate have air between the particles, so the dry total is larger than the volume you pour.
Each ingredient = dry volume × its share of the mix parts. For M15 (1:2:4, 7 parts total): cement = dry volume ÷ 7, sand = 2 × dry volume ÷ 7, aggregate = 4 × dry volume ÷ 7.
Worked example: 1 cubic yard of M15, no waste: wet volume 27 cu ft, dry volume 27 × 1.54 = 41.58 cu ft. Cement 41.58 ÷ 7 = 5.94 cu ft (about 6 × 94 lb bags), sand 11.88 cu ft, aggregate 23.76 cu ft. Water at a 0.50 water–cement ratio is about 33.5 gallons.
Cement bags per cubic yard (before waste)
| Mix | Ratio | 94 lb cement bags | Typical use |
|---|---|---|---|
| M5 | 1 : 5 : 10 | 3 | Lean / blinding concrete |
| M7.5 | 1 : 4 : 8 | 4 | Blinding / plain concrete |
| M10 | 1 : 3 : 6 | 5 | Plain concrete |
| M15 | 1 : 2 : 4 | 6 | Plain concrete / foundations |
| M20 | 1 : 1.5 : 3 | 8 | Reinforced concrete |
| M25 | 1 : 1 : 2 | 11 | Reinforced concrete, higher strength |
Bag counts use the 1.54 dry-volume factor, rounded up. Typical uses are a guide only — the mix design and code govern for structural work.
Frequently asked questions
How many cement bags are in 1 cubic yard of M15 concrete?
About 6 × 94 lb bags, with 11.88 cu ft of sand and 23.76 cu ft of aggregate, before waste — using the 1.54 dry-volume factor.
How do you calculate a concrete mix ratio?
Multiply the wet volume by 1.54 for dry volume, split it by the mix parts, and convert the cement share to bags at about 1 cu ft per 94 lb bag.
How much water do I add to a concrete mix?
Start from a 0.50 water–cement ratio by weight — about 33.5 gallons per cubic yard of M15 — then adjust for aggregate moisture and the slump you need. Too much water weakens concrete.