Water Usage Calculator
Calculate total household or project water consumption from daily per-person use, people, and days.
How it works
- 1Enter the average water use per person per day in litres (typical households use 100–200 L).
- 2Set the number of people in the household or group and the number of days to cover.
- 3The calculator multiplies the three values to give total litres, then converts to cubic metres and US gallons.
Use cases
- Sizing a rainwater tank or storage cistern for off-grid living.
- Setting household conservation targets to reduce quarterly water bills.
- Estimating water supply needs for a temporary camp or construction site.
Frequently asked questions
How is total water use calculated?
Total use = litres per person per day × number of people × days. For example, 150 L × 4 people × 30 days = 18,000 L (18 m³).
What is a typical daily water use per person?
Most households in developed countries use 100–200 litres per person per day, covering drinking, cooking, bathing, and toilet flushing. The WHO minimum for basic needs is about 50 L/person/day.
How do I convert litres to cubic metres?
1 cubic metre equals exactly 1,000 litres. So 18,000 L ÷ 1,000 = 18 m³. Water bills are often issued in m³, making this conversion useful for reconciling calculated use with actual charges.
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