Cement Mix Ratio Converter
Convert between cement, sand, and gravel ratios for different concrete and mortar applications.
See recommended mixes by project type.
Select an application to see the recommended mix ratio, or enter a custom ratio to calculate material quantities.
1 bag cement (94 lb) ≈ 1 cubic foot
General purpose (1:2:3) ≈ 3000 PSI (20 MPa)
Understanding Cement Mix Ratios
Concrete is made by mixing cement, sand (fine aggregate), gravel or crushed stone (coarse aggregate), and water in specific proportions. The mix ratio determines the strength, workability, and durability of the finished concrete. Ratios are expressed as Cement : Sand : Gravel by volume. Getting the right ratio is crucial for structural integrity and longevity of any construction project.
Common Mix Ratios by Application:
| Application | Ratio (C:S:G) | Approx. Strength | Description |
|---|---|---|---|
| General purpose | 1:2:3 | 3000 PSI (20 MPa) | Driveways, sidewalks, patios |
| Foundation / structural | 1:1.5:3 | 4000 PSI (28 MPa) | Footings, foundation walls |
| High strength | 1:1:2 | 5000+ PSI (35+ MPa) | Columns, beams, heavy loads |
| Lean mix / fill | 1:3:6 | 1500 PSI (10 MPa) | Backfill, non-structural |
| Post holes | 1:2:4 | 2500 PSI (17 MPa) | Fence posts, mailbox posts |
| Mortar (no gravel) | 1:3:0 | — | Bricklaying, stone walls |
| Rendering mortar | 1:4:0 | — | Plaster, wall rendering |
| Floor screed | 1:3:0 to 1:4:0 | — | Floor leveling |
Water-to-Cement Ratio:
The amount of water affects both workability and final strength. The general rule is 0.45 to 0.60 parts water per part cement by weight.
Water (liters) = Cement weight (kg) × water-to-cement ratio
- 0.45 ratio: Strong but hard to work with, best for structural elements
- 0.50 ratio: Good balance of strength and workability
- 0.55 ratio: Easier to pour but slightly weaker
- 0.60 ratio: Very workable but reduced strength, avoid for structural use
How Much Material Do You Need?
For a 1:2:3 mix, to produce approximately 1 cubic meter (35.3 cubic feet) of concrete, you need:
- Cement: approximately 320 kg (7 bags at 94 lb each in the US, or 6.4 bags at 50 kg each)
- Sand: approximately 640 kg (0.44 cubic meters)
- Gravel: approximately 1250 kg (0.88 cubic meters)
- Water: approximately 160 liters (42 gallons)
Practical Examples:
- A 4-inch thick sidewalk that is 3 feet wide and 20 feet long needs about 0.74 cubic yards of concrete. Use a 1:2:3 mix for a durable surface.
- Setting a 4x4 fence post requires about 2-3 bags (60-90 lb) of premixed concrete per post hole, using a 1:2:4 equivalent mix.
- A brick wall uses mortar at a 1:3 cement-to-sand ratio. One bag of cement (94 lb) mixed with 3 parts sand makes enough mortar for approximately 35-40 standard bricks.
Tips:
- Always mix dry ingredients thoroughly before adding water.
- Add water gradually and mix well. You can always add more water, but you cannot remove it.
- Concrete reaches about 70% of its full strength after 7 days and 99% after 28 days.
- In hot weather, concrete sets faster and may need more water. In cold weather, it sets slower and may need protection from freezing.