Water Heater Sizing Calculator
Estimate water heater gallon size for your household.
A water heater sizing calculator estimates the tank capacity your household needs from peak-hour hot-water demand. As a guide, estimate about 12 gallons per person plus about 10 gallons per shower, then calculate a tank size of roughly the first-hour rating multiplied by 0.7.
Recommended tank
48
gallons
First-hour rating
68
gallons/hr
Common size
50 gal
standard tank
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How does the water heater sizing calculator work?
Estimate peak-hour demand: ~12 gallons per person plus ~10 gallons per shower. Tank size ≈ first-hour rating × 0.7.
What else do people ask about this calculator?
What size water heater for a family of 4?
A 50-gallon tank with a 65-gallon first-hour rating covers most 4-person households with 2 morning showers.
Tankless or tank?
Tankless never runs out but limits simultaneous fixtures by GPM. Tanks are cheaper upfront and easier to install.
Which related calculators should I use next?
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