Water Tank Size Calculator
Estimate household or site water-storage capacity from users, daily consumption, autonomy days, reserve and usable tank percentage.
Default project preview
733 gallons
Full tanks
2
Purchased capacity
1,000 gal
Usable stored water
900 gal
Supply duration
4.5 days
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Water demand = users × daily use × autonomy days. Reserve is added, then divided by usable tank percentage. Tank count rounds up to full modules.
BuildMeter Guides
Understand the measurements and assumptions
Use these visible reference guides before changing project inputs or planning allowances.
FAQ
Water Tank Size Calculator questions
Why is usable capacity less than tank capacity?+
Outlet elevation, sediment space, overflow level and operating limits can prevent use of the full nominal volume.
How heavy is a full water tank?+
One litre of water weighs about one kilogram, and one US gallon weighs about 8.34 pounds, before tank weight.
Does this size the pump?+
No. Pump selection depends on flow, pressure, elevation, pipe loss and duty cycle.