Free Fixture Unit Calculator
Add up water supply fixture units (WSFU) for residential or commercial buildings to determine pipe sizing requirements.
Total Fixture Units
15.5 WSFU
Estimated Peak Demand19.7 GPM
Total Fixture Units vs Toilets (Flush Valve)
Fixture Unit Method
Each plumbing fixture is assigned a unit value based on its flow demand. The total WSFU determines minimum pipe size per code tables. A quick estimate for peak demand in GPM uses the Hunter curve approximation: GPM = 5 x sqrt(WSFU).
Example Calculation
2 toilets, 3 sinks, 2 showers, 1 dishwasher, 1 washer.
- 01Toilets: 2 x 2.5 = 5
- 02Sinks: 3 x 1 = 3
- 03Showers: 2 x 2 = 4
- 04Dishwasher: 1 x 1.5 = 1.5
- 05Washer: 1 x 2 = 2
- 06Total = 15.5 WSFU
- 07Peak GPM = 5 x sqrt(15.5) = 19.7 GPM
Frequently Asked Questions
Learn More
How to Calculate Concrete Needed for Any Project
Learn how to calculate the exact amount of concrete needed for slabs, footings, columns, and other projects. Covers volume formulas, waste factors, and ordering tips.