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Water Calculators

Overhead and sump tank sizing from household demand.

1 calculator Formula shown Free forever
Quick Answer

The tank calculator sizes an overhead tank from the number of people at home. It uses 135 litres per person per day, the IS 1172 and NBC 2016 figure for homes with full flushing plumbing.

Source: IS 1172, Code of Basic Requirements for Water Supply, Drainage and Sanitation (Bureau of Indian Standards), checked Jul 2026.

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Water Tank Size Calculator

Size your overhead tank from household demand, using NBC norms.

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About our water calculators

A house's water storage gets sized once and lived with for decades. Undersize the tank and you run dry every summer; oversize it and you pay for dead storage and stale water. The tank calculator sizes storage from your household's actual demand, using the NBC 2016 per-person norm, and shows the working.

Size a tank from your householdPeople in the house, times 135 litres a day each, times days of storage, rounded up to the next tank size; a family of four with two days needs 1,080 litres, so a 1,500 litre tank.1People who live in the house2× 135 L each a dayIS 1172, NBC 20163× days of storage4Round up to the next tank sizeFour people, 2 days: 1,080 L, so 1,500 L
Size a tank from your household. The water tank calculator does this arithmetic and shows the working.