Pool Heater Sizing Calculator
Estimate the heating capacity your pool may require based on pool surface area and the temperature increase you want to maintain. Use the estimated BTU requirement as a starting point when comparing pool heaters.
Estimate Your Pool Heater Size
Calculate a preliminary heating-capacity estimate using pool surface area and the difference between desired water temperature and outdoor temperature.
Your Preliminary Heating Estimate
For a 450-square-foot pool and a 20°F temperature difference, this simplified method estimates 135,000 BTU/hr of heating capacity.
This is a preliminary comparison estimate, not an engineered heat-loss calculation or a guaranteed equipment size. Wind, humidity, nighttime conditions, pool covers, desired heating time and local climate can significantly change heating requirements.
The estimate represents heating capacity, not necessarily the fuel input rating shown on a gas heater. Check manufacturer performance data and efficiency ratings before choosing a heater. Heat-pump output also varies with operating conditions.
How the Pool Heater Sizing Calculator Works
The calculator uses pool surface area and the difference between the desired water temperature and outdoor temperature to estimate heater input capacity.
Pool Surface Area × Temperature Rise × 15 = Approximate BTU/hr Input
For example, a 30-by-15-foot pool has 450 square feet of surface area. Maintaining a 20°F temperature difference produces an estimated heater input of 135,000 BTU per hour using this method.
This is a starting estimate rather than a final equipment specification. Wind, humidity, nighttime temperatures, elevation, sun exposure, pool covers, desired heating speed, and other conditions can significantly affect heating requirements.
For a more detailed explanation of BTU requirements and the factors that affect heater selection, see What Size Pool Heater Do I Need?
If you need to estimate your pool's water volume first, use the Pool Volume Calculator. After estimating heater size, you can use the Pool Heater Operating Cost Calculator to compare potential heating costs.
For more information about gas heaters, heat pumps, sizing, efficiency, and heating performance, see our Complete Guide to Pool Heaters.
Once you have an approximate heating requirement, compare available heaters while checking the exact model's BTU capacity, energy source, installation requirements, plumbing, and manufacturer specifications.