Calculate cement, sand, and gravel quantities by mix ratio. Enter total volume and ratio to get individual material amounts.
When mixing concrete from raw materials — cement, sand (fine aggregate), and gravel (coarse aggregate) — the mix ratio determines both the strength and workability of the finished product. Common ratios like 1:2:3 (one part cement to two parts sand to three parts gravel) produce approximately 3,000 PSI concrete, while richer mixes like 1:1:2 achieve 4,000+ PSI.
This calculator takes your total concrete volume and a specified mix ratio, then computes the individual volumes of cement, sand, and gravel needed. It also converts cement volume to bags (1 bag = 1 cubic foot) and shows the approximate water requirement based on standard water-cement ratios.
Site-mixed concrete is common in developing countries, remote locations, and small specialty pours where ready-mix isn't available. Understanding mix ratios ensures consistent quality when you're batching on site.
Understanding this metric in quantitative terms allows construction professionals to compare design alternatives, evaluate cost-effectiveness, and select the optimal approach for each project.
Site-mixing from raw materials requires precise proportioning to achieve the target strength. Too much water or too little cement produces weak concrete; too much cement wastes money. This calculator eliminates the guesswork by converting your project volume into exact material quantities for any standard ratio. Accurate figures enable contractors to prepare competitive bids with confidence, reducing the risk of underestimating costs or overcommitting on project timelines and deliverables.
Total parts = Cement ratio + Sand ratio + Gravel ratio Cement volume = Total volume × (Cement ratio / Total parts) × 1.54 Sand volume = Total volume × (Sand ratio / Total parts) × 1.54 Gravel volume = Total volume × (Gravel ratio / Total parts) × 1.54 (1.54 is the dry-to-wet volume factor)
Result: 25.67 ft³ cement (26 bags)
For 100 ft³ of 1:2:3 concrete: total parts = 6. Cement = 100 × 1/6 × 1.54 = 25.67 ft³ (26 bags at 94 lb each). Sand = 51.33 ft³ (1.90 yd³). Gravel = 77.00 ft³ (2.85 yd³).
M15 (1:2:4) produces approximately 2,200 PSI — suitable for foundations and mass concrete. M20 (1:1.5:3) produces approximately 2,900 PSI — the most commonly used general-purpose mix. M25 (1:1:2) produces approximately 3,600 PSI — used for structural elements. M30 and above require lab-designed mix proportions.
The water-cement ratio is the single most important factor in concrete strength. Lower ratios produce stronger concrete but are harder to work with. Aggregate size and shape also affect strength — well-graded, angular aggregates produce stronger concrete than round, gap-graded ones.
Site-mixed concrete makes sense for remote locations, small specialty batches, and developing regions without ready-mix plants. For most construction in developed areas, ready-mix provides better quality control, labor savings, and consistent results.
It means 1 part Portland cement, 2 parts sand (fine aggregate), and 3 parts gravel (coarse aggregate) by volume. This is the most common general-purpose concrete mix, producing approximately 3,000 PSI.
Higher cement content produces stronger concrete. A 1:1:2 ratio produces approximately 4,500+ PSI. However, more cement also means more cost and more heat during curing. Follow your engineer's mix design for structural work.
A typical water-cement ratio of 0.45–0.50 by weight is used. For one 94-lb bag of cement, that's about 5–6 gallons of water. Too much water weakens the concrete; too little makes it unworkable.
When you mix dry cement, sand, and gravel, the fine particles fill voids between larger particles. The final volume of mixed concrete is about 65% of the total dry material volume, so you need 1.54 times more dry material (1/0.65 = 1.54).
Cement mixed with sand only (no coarse aggregate) produces mortar or sand-cement mix, not concrete. Mortar is weaker than concrete and suitable for bricklaying, plastering, and small repairs — not structural work.
Use a consistent container (like a 5-gallon bucket) to measure each material by volume. One bucket of cement, two buckets of sand, three buckets of gravel gives you a 1:2:3 ratio. Consistency is key.