Plumbing Tools

Water Heater Size Calculator

Calculate gallons or BTU needed for tank or tankless water heaters. Based on occupants, fixtures, and usage patterns.

Household Requirements

Number of Occupants

Heater Type

Number of Bathrooms

Peak Hour Demand (gallons)

Incoming Water Temp (°F)

Target Temp (°F)

Fuel Type

Efficiency Factor

                                Recommended Size
                                0
                                gal
                            

First Hour Rating 0 gal

Peak Hour Demand 0 gal

Temperature Rise Needed 70°F

Required BTU/Input 0 BTU

Recovery Rate (at 90°F rise) 0 GPH

Annual Energy Cost (est) $0

Est. Heater Cost $0

Tank: Peak demand + 10-20 gal buffer

Tankless: GPM × Temp Rise × 500

First Hour: Tank size × 0.7 + Recovery

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