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Water Heater Size Calculator

Estimate first-hour rating from showers and fixtures.

Add showers, baths, sinks, dishwasher, and laundry in the busiest hour.

How this calculation works

Peak-hour demand and tank size.

People in home

Showers in peak hour

Minutes per shower

Shower flow (gpm)

Tubs filled in peak hour

Dishwasher in peak hour?

Clothes washer in peak hour?

Stacks to cords and face cords.

Gallons by pool shape.

Room area, tile size, waste, and boxes.