BTU Calculator
Heating and cooling capacity a room needs.
Enter your values
ⓘ Live results
Results
- Cooling capacity needed
- 8,000 BTU/hr
- In tons of cooling
- 0.67
- Heating capacity (rough)
- 12,000 BTU/hr
- In kilowatts
- 2.34 kW
Quick answer
A rough baseline is 20 BTU per square foot for cooling, adjusted for ceiling height, sunlight and insulation quality.
BTU ≈ area × 20 × adjustment factors
How to use the BTU Calculator
- 1Enter the room area and ceiling height.
- 2Pick sun exposure and insulation quality.
- 3Read the BTU capacity to shop for.
Worked example
Using the values the calculator loads with:
Inputs
- Room area400 sq ft
- Ceiling height8 ft
- Sun exposureAverage
- InsulationAverage
- People usually in the room2
Results
- Cooling capacity needed8,000 BTU/hr
- In tons of cooling0.67
- Heating capacity (rough)12,000 BTU/hr
- In kilowatts2.34 kW
Frequently asked questions
Is a bigger unit better?
No. An oversized AC short-cycles, cooling fast without removing humidity, which leaves the room clammy.
How many BTU is a ton?
12,000 BTU per hour — the rate at which a ton of ice melts in 24 hours.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.