How does the water demand calculator work?

It multiplies the number of occupants by the water use per person per day (LPCD) to get total daily demand in litres. That figure is then divided by 1000 for cubic metres per day, and multiplied by 365 and divided by 1000 for annual demand in kilolitres. For example, 5 occupants at 135 LPCD works out to about 675 litres a day.

What LPCD value should I enter for occupants?

LPCD means litres per capita per day. A figure of 135 LPCD is a commonly-cited domestic design norm in India for homes with full plumbing, and the tool defaults to it. Water-scarce or basic-service areas may use lower values, while premium homes with more fixtures may need more. Set occupants to the real people the building serves daily and adjust LPCD to match your standard.

How accurate is the daily water demand figure?

Treat it as indicative sizing for concept planning, not a final design value. The base 135 LPCD norm covers everyday domestic use but excludes gardens, swimming pools, cooling towers and system losses, so real demand can be higher. Before you procure tanks, sumps or supply, confirm the figure against NBC 2016 Part 9 and your local water body's standards, or with a plumbing engineer.

Interactive Calculator · 2026

Building Water Demand Calculator

Estimate a home or building's total daily water demand for design. Enter the number of occupants and the water use per person (LPCD) — get the daily demand in litres and m³ plus the annual demand in kilolitres to size tanks, sumps and supply.

Daily water demand (5 occupants · 135 LPCD)0 L/day≈ 0.00 m³/day · 0.0 kL/year

Typical breakdown (illustrative) of the daily demand across end uses

Your building

Number of occupants (persons)

Total people the building serves daily.

Water use per person (LPCD)

Litres per capita per day — design norm.

Water use per person (LPCD)135 LPCD

135 LPCD is a commonly-cited domestic design norm — editable. Verify against NBC 2016 Part 9 or your local body's standard.

Daily demand

0 L/day

Daily demand

0.00 m³/day

Annual demand

0.0 kL/year

Where the water goes (illustrative)

A typical split of domestic demand across end uses — actual shares vary by household and fittings.

At 5 occupants and 135 LPCD, the building needs about 675 litres a day — roughly 0.68 m³. Over a year that is 246.38 kilolitres, the figure to plan storage and metered supply against.

The split above is illustrative — bathing and flushing usually dominate, so efficient fixtures cut demand the most.

How this is calculated

Daily demand (L) = occupants × LPCD = 5 × 135 = 675 L/day.
Daily demand (m³) = daily litres ÷ 1000 = 675 ÷ 1000 = 0.68 m³/day.
Annual demand (kL) = daily litres × 365 ÷ 1000 = 675 × 365 ÷ 1000 = 246.38 kL/year.

Indicative sizing for concept planning; 135 LPCD is a commonly-cited domestic design norm but excludes gardens, pools and losses — confirm the demand figure against NBC 2016 Part 9 and your local body before procurement.

Understand the number you just got

Water Supply Systems in IndiaHow buildings source, store and distribute water — sumps, tanks and mains.Plumbing Design Checklist (India)From demand to layout — the design decisions that follow this number.

Frequently asked questions

How does the water demand calculator work?: It multiplies the number of occupants by the water use per person per day (LPCD) to get total daily demand in litres. That figure is then divided by 1000 for cubic metres per day, and multiplied by 365 and divided by 1000 for annual demand in kilolitres. For example, 5 occupants at 135 LPCD works out to about 675 litres a day.
What LPCD value should I enter for occupants?: LPCD means litres per capita per day. A figure of 135 LPCD is a commonly-cited domestic design norm in India for homes with full plumbing, and the tool defaults to it. Water-scarce or basic-service areas may use lower values, while premium homes with more fixtures may need more. Set occupants to the real people the building serves daily and adjust LPCD to match your standard.
How accurate is the daily water demand figure?: Treat it as indicative sizing for concept planning, not a final design value. The base 135 LPCD norm covers everyday domestic use but excludes gardens, swimming pools, cooling towers and system losses, so real demand can be higher. Before you procure tanks, sumps or supply, confirm the figure against NBC 2016 Part 9 and your local water body's standards, or with a plumbing engineer.

Related Guides — Deep-dive reading

Water Consumption Estimation for Buildings: LPCD Norms, Occupancy & End-Use Breakdown

How to estimate a building's daily water demand from its occupancy and NBC per-capita norms, break it down by end use, and turn that number into the foundation for sizing water supply, storage and sewage systems.

Sewage Treatment Plants

Water Supply Systems in India: How Water Reaches Every Tap in Your Home

The complete map of how water gets into an Indian home and out to every fixture — the sources it comes from, the sump-pump-overhead-tank storage model that buffers intermittent supply, how gravity and pressurised distribution differ, and the demand figures that size the whole thing.

Plumbing

Plumbing Design Checklist for Indian Buildings (Stage-by-Stage)

A practitioner's stage-by-stage plumbing design checklist — from water demand and storage sizing to distribution, drainage, rainwater harvesting, structural coordination and compliance sign-off.

Plumbing

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