Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Demand inputs must match the application. Not a drinking-water quality, firefighting flow or legal storage standard.
Example Calculation
- People served: 20
- Daily demand per person: 100 L/person/day
- Other daily demand: 500 L/day
- Reserve duration: 2 days
- Contingency: 10 %
20 people at 100 L/day plus 500 L other use need 2500 L/day; a two-day reserve with 10% contingency is 5.5 m³.
Frequently asked questions
How do I use this calculator?
Enter people served, daily demand per person, other daily demand, reserve duration, contingency. The result updates automatically. Use Reset to restore the example values.
What method does it use?
daily demand=people × per-person use+other; storage=daily demand × days × (1+contingency).. Demand inputs must match the application. Not a drinking-water quality, firefighting flow or legal storage standard.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.