Pool heater BTU calculator
PROBTU/hr to heat a pool to your target temperature.
Short answer: BTU/hr = (gal × 8.34 × ΔT) ÷ hours. 20,000 gal × 20°F ÷ 24 hr = 139,000 BTU/hr. Enter your measurements above and the pool heater btu calculator returns the quantity, unit conversions and an estimated cost instantly, in imperial or metric — no sign-up needed.
What do you need to measure?
What is the answer?
BTU/hr
139,000
Heater size (nearest 50k)
150k BTU
How does the pool heater btu calculator work?
BTU/hr = (gal × 8.34 × ΔT) ÷ hours.
What does a worked example look like?
20,000 gal × 20°F ÷ 24 hr = 139,000 BTU/hr.
What do people ask most?
›Gas vs heat pump?
Gas heats fast; heat pumps are 4–5× more efficient long-term.
Which pool calculator should you use next?
Where can you learn more?
Read field notes on estimating and materials, or browse every calculator we make.