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Water Use Intensity Calculator

Work out water use intensity instantly with clear inputs, formula shown and shareable results.

About Water Use Intensity Calculator

Water use intensity can be normalised by area or by occupancy, and for an office the per-occupant figure is the more diagnostic: most consumption is sanitary and therefore tracks people, not floor plate. Fifty litres per person per working day is efficient, over eighty suggests leaks or inefficient fittings.

Formulas

Per occupant

Litres per person per day = annual kL x 1000 / (occupants x working days)

Per area

kL/m²/year = annual kL / area in m²

Worked example

With the default values below, Water Use Intensity Calculator returns Water per occupant per working day of 120.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Annual water consumptionminimum 0 kL
12,000 kL
Gross floor areaminimum 0.1 ft²
60,000 ft²
Occupantsminimum 1
400

Results

Water per occupant per working day
120.0 L
Water use intensity
2.153 kL/m²/year
Intensity per square foot
0.2000 kL/ft²/year
Average daily consumption
32.88 kL

Step by step

  1. 1Values used
  2. 2Per occupant
  3. 3Per area
  4. 4Water per occupant per working day= 120.0 L
  5. 5Water use intensity= 2.153 kL/m²/year
  6. 6Intensity per square foot= 0.2000 kL/ft²/year
  7. 7Average daily consumption= 32.88 kL

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or fees or charges into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Water Use Intensity figure worked out?

Litres per person per day = annual kL x 1000 / (occupants x working days). Water use intensity can be normalised by area or by occupancy, and for an office the per-occupant figure is the more diagnostic: most consumption is sanitary and therefore tracks people, not floor plate.

What if the building has cooling towers?

Evaporative cooling can double total consumption and it tracks weather, not occupancy. It should be sub-metered and reported separately from domestic use.

What values do I need to enter?

This calculator takes 3 inputs: Annual water consumption, Gross floor area, Occupants. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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