300 ft2 room
- Base table value
- 7000 BTU/h
- Adjusted estimate
- 7000 BTU/h
- Ceiling height
- 8 ft
Oversized air conditioners can cool without dehumidifying well. Use this as a shopping estimate, not HVAC design.
BTU Calculator
Use this free BTU calculator to estimate room cooling capacity from square feet, ceiling height, sunlight, people, and kitchen heat load.
Research-backed assumptions Formula steps Examples included Private in-browser use
Formula steps
- Start with a room-size BTU table for an 8-foot ceiling.
- Adjust for ceiling height, sun exposure, people, and kitchen heat when selected.
- Round to a practical 500 BTU increment.
How to use the btu calculator
- Enter room square feet, ceiling height, sunlight level, people, and kitchen setting.
- Press Estimate BTU to get an approximate room air conditioner cooling capacity.
- Use the notes to understand why oversized units can still be uncomfortable.
- Use professional HVAC sizing for whole-home or high-stakes cooling decisions.
Common uses
Estimate a window or room air conditioner size.
Adjust for sunny or shaded rooms.
Account for extra people and kitchen heat.
Avoid buying a unit that is wildly under- or oversized.
Examples
Approximate room BTU
Adjusted BTU estimate
Higher BTU estimate
Frequently asked questions
Plain-language answers about when to use the tool, what it does with your inputs, what to double-check, and how privacy works.
When should I use the BTU Calculator?
Use it when your task matches one of these common needs: Estimate a window or room air conditioner size. Adjust for sunny or shaded rooms. It works best when you already know the values, dates, units, or settings the page asks for.
What is the BTU Calculator doing with my inputs?
In plain language: The calculator starts with a room-size BTU table, adjusts for ceiling height, sunlight, extra people, and kitchen heat, then rounds to a practical BTU amount. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
What should I double-check before trusting the answer?
This is a room AC shopping estimate, not a full HVAC load calculation. Insulation, climate, windows, ducts, and humidity matter. Also check that you used the right unit, date, scale, or mode because small input changes can change the result.
Does the site save what I enter?
No. The calculator runs in your browser tab. Your recent answers stay only on the page while you use it, and they are not sent to a server.
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