Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Gallons per sq ft / year
20.00
Gallons per employee / year
5,455
Annual water + sewer cost
$11,400
Average gallons per day
3,288
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter annual water use (gallons).
- 2Enter building square footage (sq ft).
- 3Enter average headcount.
- 4Enter cost per 1,000 gallons (water + sewer) ($).
- 5Read your gallons per sq ft / year on the right — it updates as you type.
- 6Hit Share to keep the scenario or send it to someone.
About this calculator
Water use intensity normalizes total water consumption by building area or occupancy so you can compare a 20,000 sq ft office to a 200,000 sq ft one on equal footing, and track year-over-year efficiency independent of growth. This calculator takes your annual water bill volume and computes both gallons per square foot and gallons per employee, the two metrics most commonly requested in ESG questionnaires (CDP Water Security, GRESB) and LEED water-efficiency credits. Office buildings without cooling towers or process water typically run 10-20 gallons per sq ft per year; add a cooling tower, commercial kitchen, or laundry and that number climbs sharply. Tracking this over time is how facilities teams catch leaks — a WUI that jumps 20% without a corresponding occupancy change is usually a leak or fixture failure, not a real usage increase.
Worked example
Using the values the calculator loads with:
Inputs
- Annual water use: 1200000 gallons
- Building square footage: 60000 sq ft
- Average headcount: 220
- Cost per 1,000 gallons (water + sewer): 9.5 $
Results
- Gallons per sq ft / year: 20
- Gallons per employee / year: 5,455
- Annual water + sewer cost: $11,400
- Average gallons per day: 3,288
What each field means
Inputs
- Annual water use (gallons)
- The annual water use used in the calculation, measured in gallons. Starts at 1200000 gallons so you have a working example on load.
- Building square footage (sq ft)
- The building square footage used in the calculation, measured in sq ft. Starts at 60000 sq ft so you have a working example on load.
- Average headcount
- The average headcount used in the calculation. Starts at 220 so you have a working example on load.
- Cost per 1,000 gallons (water + sewer) ($)
- The cost per 1,000 gallons (water + sewer) used in the calculation, measured in $. Starts at 9.5 $ so you have a working example on load.
Results
- Gallons per sq ft / year
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Gallons per employee / year
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Annual water + sewer cost
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Average gallons per day
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
What's a good WUI benchmark for an office building?
A typical US office without cooling towers runs 10-20 gallons per sq ft per year, dominated by restroom fixtures and kitchen use. Buildings with evaporative cooling towers can see this double or triple because cooling towers consume water continuously through evaporation and blowdown.
How do I use this for CDP Water Security disclosure?
CDP asks for total water withdrawal and consumption, often normalized by revenue or floor area. Reporting gallons per sq ft alongside your absolute volume gives reviewers the intensity trend they're looking for, and it's the same metric LEED v4 Water Efficiency credits use for baseline comparison.
My WUI jumped significantly year over year — what should I check first?
Check for running toilets and irrigation controller failures first — these are the two most common causes of unexplained spikes and are usually invisible until the bill arrives. A submeter on major fixture groups (restrooms, kitchen, irrigation, cooling tower) makes root-causing this much faster than working from one aggregate number.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
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Scope 1 & 2 Emissions Calculator
Estimate direct and purchased-energy emissions from utility bills.
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Water Use Intensity Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/water-use-intensity
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/water-use-intensity" target="_blank" rel="noopener">Water Use Intensity Calculator — RevenueLab</a> (2026).</p>
Source: [Water Use Intensity Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/water-use-intensity) (2026).