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Water Heater Sizing Calculator

Tank size in gallons by household size.

Estimate the tank size (gallons) and recommended first-hour rating for a household water heater, based on the number of people in the home.

Nadia Almasri By Nadia Almasri
Published Last reviewed 1 min read

Inputs

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

Recommended tank ≈ 20 gal for the first person + 10 gal per additional person. First-hour rating ≈ tank × 1.6.

In depth

Estimate the tank size (gallons) and recommended first-hour rating for a household water heater, based on the number of people in the home.