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.
- No inflow during the modeled interval. Does not assess potable-water quality, overflow, supports or fire reserves.
Example Calculation
- Daily draw: 500 L/day
- Maximum refill interval: 3 days
- Unavailable bottom volume: 100 L
- Demand contingency: 20 %
Daily draw = 500 L/day; Maximum refill interval = 3 days; Unavailable bottom volume = 100 L; Demand contingency = 20 %. Primary result: 1900.
Frequently asked questions
How do I use this calculator?
Enter daily draw, maximum refill interval, unavailable bottom volume, demand contingency. The result updates automatically. Use Reset to restore the example values.
What method does it use?
tank volume=daily draw ×interval ×(1+contingency)+unavailable volume.. No inflow during the modeled interval. Does not assess potable-water quality, overflow, supports or fire reserves.
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.