What is the Water Tank Calculator?
A water tank calculator recommends the right capacity for your home based on the number of occupants and daily water usage per person (IS 1172 suggests 135 L/person/day for residential dwellings).
It also suggests rough physical dimensions for a cuboid or cylindrical tank to hold that volume.
Formula
Capacity (L) = Persons × Litres/person/day · Volume (m³) = Capacity / 1000
- Persons — Total household members
- Litres/person/day — 135 L (IS 1172) for full residential use
Keep 1.5–2 days of buffer for areas with intermittent supply.
Step-by-step example
Setup: 4 persons, 135 L/person/day, cuboid tank.
- Daily = 540 L
- Volume = 0.54 m³
- Cube side ≈ 0.81 m
Answer: ≈ 540 L tank · ≈ 0.81 × 0.81 × 0.81 m cube (use 1000 L standard for safety)
Frequently asked questions
Why use a bigger tank than daily usage?
Municipal supply often runs for only a few hours a day. A 2-day buffer protects against outages.