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 air conditioner cooling capacity from square feet, ceiling height, sunlight, people, and kitchen heat load.
Inputs explainedResult checksExample valuesRuns in your browser
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.
Examples
Recent answers
Recent BTU estimates will appear here.
BTU estimates use room sizing assumptions in your browser and do not replace a professional HVAC load calculation.
Inputs and recent answers stay in this browser tab and are not sent to a server.
How to use the BTU Calculator
- Enter room square feet, ceiling height, sunlight level, people, and kitchen setting.
- Press Estimate BTU to see base BTU, adjusted BTU, and the rounded BTU/h recommendation.
- Use the result as a room air conditioner shopping estimate, not a whole-home HVAC design.
- Use professional HVAC sizing when insulation, windows, climate, ducts, or expensive equipment matter.
What people use it for
Estimate a window or portable room air conditioner size before shopping.
Compare bedroom, living-room, and kitchen cooling needs.
Adjust a room estimate for sunny or shaded exposure.
Account for extra regular occupants and kitchen heat.
Sanity-check an AC product label against the room you actually need to cool.
Decide when the room is unusual enough to need a professional load calculation.
Quick examples
Bedroom
180 ft2, 8 ft ceiling, normal sun, 2 people6,000 BTU/h recommended
Sunny living room
420 ft2, 9 ft ceiling, sunny, 3 people13,000 BTU/h recommended
Kitchen area
300 ft2, 8 ft ceiling, kitchen heat selected11,000 BTU/h recommended
Shaded small room
150 ft2, 8 ft ceiling, shaded4,500 BTU/h recommended
Tall larger room
500 ft2, 10 ft ceiling, 4 people16,000 BTU/h recommended
Need the guide or a nearby tool?
Need a slower walkthrough, a related calculator, or the full library? These links keep you close to the task you started.
- How to use the BTU CalculatorSee slower examples, input meanings, formula notes, result limits, and mistakes to avoid.
- Everyday ToolsBrowse related calculators and utilities in the same category.
- Calculator and utility guidesFind more guides that use real tool inputs and example numbers.
- All free toolsSearch every live tool, converter, calculator, AI helper, and browser utility.
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 portable room air conditioner size before shopping. Compare bedroom, living-room, and kitchen cooling needs. It works best when you already know the measurements, amounts, units, or options 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 for an 8-foot ceiling, scales for ceiling height, reduces shaded rooms by 10%, adds 10% for sunny rooms, adds 600 BTU/h for each regular person above two, adds 4,000 BTU/h for kitchen heat, then rounds to the nearest 500 BTU/h. The examples on the page are there so you can compare your inputs with a worked example before copying the answer.
What do the main BTU Calculator inputs mean?
Room square feet: the floor area of the room you want to cool. Ceiling height: the room height. Taller rooms have more air volume than a normal 8-foot room. Sunlight: whether the room is normally shaded, average, or sunny. Regular people in room: the usual number of people in the room. The estimate adds heat load when more than two people regularly use it. Kitchen heat load: extra cooling demand from cooking appliances and kitchen heat.
How should I read the BTU Calculator answer?
Read the headline answer, then check the smaller lines beside it. For everyday tools, those lines usually show the distance, time, cost, units, or setting that made the answer change.
What should I double-check before trusting the answer?
This is a room AC shopping estimate, not a Manual J or whole-home HVAC load calculation. Insulation, climate, window area, air leakage, ducts, humidity, and equipment efficiency can change the real load. Also check the unit, scale, mode, and result limit because small input changes can change the answer.
What does BTU/h mean for an air conditioner?
BTU/h means British thermal units per hour. For a room air conditioner, it is a cooling-capacity rating: about how much heat the unit can remove from the room in one hour.
How does room square footage affect the BTU estimate?
The calculator starts with a room-size table. For example, 180 square feet starts from 6,000 BTU/h, while 420 square feet starts from 10,000 BTU/h before sunlight, ceiling height, people, or kitchen adjustments.
Why does ceiling height change the result?
A taller room has more air volume than an 8-foot room with the same floor area. The calculator scales the base estimate by ceiling height divided by 8.
Why do sunny rooms need more BTU?
Direct sun can add heat through windows, walls, and the roof. This calculator adds 10% for sunny rooms and subtracts 10% for shaded rooms as a simple shopping adjustment.
Why does kitchen heat add 4,000 BTU/h?
Cooking appliances, ovens, dishwashers, and extra activity can add a lot of heat. The calculator uses a simple 4,000 BTU/h kitchen adjustment so a kitchen or open kitchen area is not undersized.
Why is a bigger BTU number not always better?
An oversized room air conditioner can cool the air quickly but cycle off before removing enough humidity. That can make the room feel cold and clammy instead of comfortable.
Is this a full HVAC load calculation?
No. It is a room air conditioner shopping estimate. Use a professional load calculation when the decision involves central HVAC, ducts, unusual insulation, many windows, high humidity, or expensive equipment.
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.