Free Water Heater Sizing Calculator
Estimate the tank size and BTU input needed for a residential water heater based on household demand.
people
gal
degF
hr
Recommended Tank Size
80 gal
BTU Input Needed46,648 BTU/hr
Daily Hot Water Demand80 gal
Recommended Tank Size vs Number of Occupants
Water Heater Sizing
Daily Demand = Occupants x Gallons per Person
BTU/hr = Demand x 8.33 x Temp Rise / Recovery Hours
The constant 8.33 is the weight of one gallon of water in pounds. Tank size is rounded up to the nearest standard 10-gallon increment.
Example Calculation
A household of 4 using 20 gallons each, 70 degF rise, 1-hour recovery.
- 01Daily demand = 4 x 20 = 80 gal
- 02Tank size = round up to 80 gal
- 03BTU = 80 x 8.33 x 70 / 1 = 46,648 BTU/hr
Frequently Asked Questions
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