Air Conditioner BTU Calculator
Use this air conditioner BTU calculator to estimate a recommended cooling capacity from room size and common adjustments such as people, ceiling height, room type, and sun exposure.
BTU/h
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Result
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Quick Answer: A room's recommended BTU starts from floor area and is then adjusted for room type, sunlight, extra occupants, and ceiling height. Omni's room-size ranges are paired with 600 BTU per additional person above two and 1000 BTU per extra foot above an 8-foot ceiling.
How to Calculate
- Measure room length and width: Multiply length by width to get the room area in square feet.
- Determine the base BTU range: Use the room area against the standard BTU sizing table before any adjustments.
- Apply room and occupancy adjustments: Kitchen use, extra people, and high ceilings increase the cooling recommendation.
- Apply the sun factor: Shaded rooms reduce the requirement slightly, while sunny rooms increase it.
Formula
Recommended BTU = (base room BTU + room adjustment + people adjustment + ceiling adjustment) x sun factor
| Variable | Meaning | Unit |
|---|---|---|
| Base BTU | Cooling capacity from room area | BTU/h |
| People adjustment | Extra cooling for people above two | 600 BTU/h per extra person |
| Ceiling adjustment | Extra cooling for ceiling height above 8 ft | 1000 BTU/h per extra foot |
| Sun factor | Room shading or sunny multiplier | 0.9, 1.0, or 1.1 |
Worked Examples
Sizing - Sunny kitchen
- Room size: 18 ft x 15 ft
- Area: 270 ft2
- Room type: Kitchen
- People: 4
- Ceiling: 9 ft
- Sun: Sunny
Result: Recommended BTU is about 13,420 BTU/h.
The kitchen adjustment, two extra people, one extra foot of height, and sunny exposure all raise the cooling requirement.
Sizing - Shaded bedroom
- Room size: 12 ft x 12 ft
- Area: 144 ft2
- Room type: Bedroom
- People: 2
- Ceiling: 8 ft
- Sun: Shaded
Result: Recommended BTU is about 4,500 BTU/h.
A small shaded bedroom needs less cooling than an equally sized sunny space.
Check current unit - Current 12,000 BTU unit
- Area: 300 ft2
- Room type: Living room
- Ceiling: 8 ft
- Sun: Neutral
- Current AC: 12,000 BTU/h
Result: The unit can typically support roughly 8 people under this simplified model.
The current-unit mode estimates how much occupant load remains after the base room requirement is met.
Interpretation Table
| Range | Meaning | Action |
|---|---|---|
| Small rooms | Lower base BTU requirement | Shading and low occupancy can reduce the final recommendation further. |
| Rooms with extra people | Higher internal heat gain | Add about 600 BTU/h for each person above two. |
| Ceilings above 8 ft | Larger room volume | Add about 1000 BTU/h for each extra foot of ceiling height. |
Frequently Asked Questions
Find the room area, determine the base BTU from the sizing table, and then apply adjustments for kitchen use, people, ceiling height, and sun exposure.
BTU is a measure of cooling capacity. A higher BTU rating means the unit can remove more heat per hour.
Yes. Taller ceilings increase the room volume, so the calculator adds cooling capacity when the ceiling is above 8 feet.
People add heat to the room, so the cooling load rises as occupancy increases.
Note: This is a room-sizing estimate, not a substitute for a detailed HVAC load calculation that considers insulation, windows, climate, infiltration, and system performance.
References
Last reviewed: March 14, 2026