Water Tank Size Calculator
Estimate water tank size in liters from household size, liters per person per day, and storage days.
Last reviewed by the Radiatus Cloud team
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Size a water tank for a household
A water tank must hold enough for a household’s needs, and sizing it prevents shortages. This calculator estimates the tank size in litres from household size, daily use per person and any reserve.
Why sizing matters
A tank too small runs dry, a tank too large costs more and takes space, so the right size is the daily consumption times the number of days you want to cover. Daily use per person, times the household size, gives the daily demand, and multiplying by the reserve days plus any buffer gives the tank size. Getting this right ensures a reliable supply between refills or through an interruption, which is exactly what a storage tank exists for. It turns a guess into a figure based on real household needs.
A planning estimate
These are estimates from a standard method for general planning, not professional advice; confirm anything important for your specific situation. It runs entirely in your browser, so nothing you enter is uploaded and it works without an account, keeping your data on your own machine.
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Frequently Asked Questions
How is tank size estimated?
From the daily water use per person times the household size, multiplied by the number of days of supply you want to cover, plus any reserve.
Why not just buy the biggest tank?
Because a larger tank costs more and takes space, and water stored too long can stagnate. The right size matches real needs plus a sensible reserve.
What is the reserve for?
Covering interruptions in supply, so the household has water through a refill delay or outage. It is added on top of daily demand.
What determines daily demand?
The number of people and their per-person daily use, which varies with lifestyle. The calculator uses your figures to size the tank.
Is my data uploaded?
No. The calculation runs entirely in your browser.
Privacy & Security
Calculated locally in your browser. No data is sent to any server.
How to Use
Enter people and storage days to estimate tank capacity.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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