Cement Water Ratio Calculator
Calculate the amount of water needed for a given number of cement bags and water-cement ratio.
Supports liters and gallons.
Water Needed
Water-cement ratio (w/c) is the ratio of water weight to cement weight. It directly affects concrete strength and workability.
Water (kg) = Cement Weight (kg) × Water-Cement Ratio
Standard cement bag sizes:
- Most countries: 50 kg per bag
- USA: 94 lbs (42.6 kg) per bag
- UK: 25 kg per bag
Recommended w/c ratios:
| Application | w/c Ratio | Approx. Strength |
|---|---|---|
| High-strength structural | 0.35–0.40 | 40+ MPa |
| General structural | 0.45–0.50 | 25–35 MPa |
| Moderate exposure | 0.50–0.55 | 20–25 MPa |
| Non-structural / paving | 0.55–0.65 | 15–20 MPa |
Water conversions:
- 1 kg of water = 1 liter
- 1 liter = 0.2642 US gallons
- 1 US gallon = 3.785 liters
Tip: Lower w/c ratios produce stronger, more durable concrete but require more careful placement and compaction.