Water volume conversions
US gallons throughout. The weights are for fresh water; salt water is slightly heavier.
| Unit | US gallons | Liters | Also equals |
|---|---|---|---|
| 1 US gallon | 1 | 3.785 | 231 cubic inches; 8.34 lb of water |
| 1 cubic foot | 7.48 | 28.32 | 1,728 cubic inches; 62.4 lb of water |
| 1 cubic meter | 264.17 | 1,000 | 35.31 cubic feet |
| 1 liter | 0.264 | 1 | 61.02 cubic inches; about 1 kg of water |
| 1 UK (imperial) gallon | 1.2 | 4.546 | Used in British pool and fish books |
| 1 inch of water over 100 sq ft | 62.3 | 236 | Handy for pool top-ups |
Quick formulas
- Pool: surface area in square feet × average depth in feet × 7.48 = gallons.
- Aquarium: length × width × height in inches ÷ 231 = gallons.
- Metric: length × width × depth in meters × 1,000 = liters, or centimeters multiplied together ÷ 1,000 = liters.
Which calculator do you need?
Use the pool volume calculator before you dose chemicals, buy a pump or fill the pool; it handles round, oval, rectangular and kidney pools with a shallow and a deep end. The aquarium volume calculator gives a tank's gallons, the water it really holds after substrate and decor, and its weight. Once you know the tank, the fish tank stocking calculator checks your fish list against the usual rules of thumb.