Reservoir Capacity Calculator
Calculate the storage volume of cylindrical or rectangular reservoirs and tanks.
How it works
- 1Choose metric or imperial units and the tank shape — cylindrical or rectangular.
- 2Enter the dimensions: diameter and height for a cylinder, or length, width, and height for a rectangle.
- 3The calculator applies π/4·d²·h or L·W·H and shows the result in m³, litres, and gallons.
Use cases
- Sizing a rainwater-harvesting tank for a home or farm.
- Estimating storage for irrigation reservoirs and farm dams.
- Verifying volume for fire-suppression water storage.
Frequently asked questions
How is cylindrical volume calculated?
V = π/4·d²·h. A 3 m diameter, 4 m tall tank holds π/4 × 9 × 4 ≈ 28.27 m³ (28,270 litres).
What is freeboard and why does it matter?
Freeboard is the gap between the water surface and the tank top (often 10–20% of height). It prevents overflow from surges and thermal expansion, so do not fill to 100% of the geometric volume.
How do I convert m³ to litres or gallons?
1 m³ = 1000 litres exactly, and ≈ 264.17 US gallons. Toggle metric/imperial to see the equivalent.
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