Get a quick recommendation for storage tank capacity or tankless flow rate based on your household size.
This calculator gives a quick recommendation for water heater sizing — either the storage tank capacity in gallons or the flow rate in gallons per minute (GPM) for a tankless unit — based on your household size.
Sizing follows standard plumbing industry rules of thumb: storage tank capacity and tankless flow rate both scale with the number of people in the household and expected simultaneous hot water use (showers, dishwasher, laundry).
A household of 3–4 people sizing a storage tank should look at roughly a 40-gallon unit, while the same household sizing a tankless unit should look for one rated at least 6 GPM.
If your household regularly runs multiple hot water fixtures at once (e.g., a shower and the dishwasher), size up to the next bracket to avoid running out of hot water.
Based on household size, peak hour demand, and the heater's recovery rate.
How many gallons of hot water a tank heater can deliver in the first hour of high demand.
Yes — sized based on maximum simultaneous flow rate needed.