Why use this calculator
Knowing the exact volume of your water storage is essential for planning livestock water supply, fire fighting reserves, and irrigation capacity. Whether you are sizing a new tank purchase or estimating the capacity of an existing dam, accurate volume calculations prevent water shortages during critical dry periods.
How to use it
Select the type of water storage (round tank, rectangular tank, or dam), then enter the relevant dimensions. For round tanks use the diameter, for rectangular tanks and dams use length and width. Enter the height or depth for all types. The calculator provides volume in litres, gallons, and cubic metres.
The formula
Round Tank: V = pi x r^2 x h. Rectangular Tank: V = l x w x h. Dam (tapered): V = l x w x h x 0.4 (approximation for sloped sides). 1 cubic metre = 1,000 litres.
Worked examples
Round tank: 3m diameter, 2.5m height
17,671 litres (17.67 cubic metres)
Farm dam: 20m x 15m x 3m depth
360,000 litres (360 cubic metres) using tapered approximation
When people use it
- Sizing water tanks for livestock drinking requirements
- Estimating farm dam capacity for irrigation planning
- Calculating fire fighting water reserve requirements
- Planning rainwater harvesting and tank storage systems
Tips
- Allow for at least 3-6 months water reserve in drought-prone areas
- Cattle require approximately 40-80 litres per head per day depending on temperature
- Include evaporation losses of 5-10mm per day when calculating dam storage duration
- Consider installing tank level indicators for remote monitoring of water supplies
Questions people ask
- Why is the dam formula different?
- Farm dams have sloped sides (batters), so the actual water volume is significantly less than a simple length x width x depth calculation. The 0.4 factor is a general approximation for typical batter slopes of 3:1 to 4:1. For precise dam volumes, a survey and engineering calculation is recommended.
- How much water do my livestock need?
- Daily water requirements per head: cattle 40-80 litres, sheep 4-10 litres, horses 35-55 litres. Requirements increase significantly in hot weather. Lactating animals may need double the base requirement.
- Should I use litres or gallons?
- In Australia and most countries using the metric system, litres and cubic metres are standard. Gallons are provided for reference. One US gallon equals approximately 3.785 litres. Water tank manufacturers typically rate capacity in litres.