Air Conditioner BTU Calculator
Calculate the optimal cooling capacity (BTU) for your room or home. Get accurate BTU estimates and tonnage recommendations based on room dimensions, occupancy, insulation, and sun exposure.
0 BTU
(0.0 tons)
This is an estimate. For a Manual J load calculation, consult an HVAC professional.
How We Calculate This
+Our calculator uses industry-standard formulas to estimate cooling requirements:
| Factor | Calculation |
|---|---|
| Base BTU | Area (sq ft) × 25 BTU/sq ft |
| Ceiling Height | +1,000 BTU per foot over 8 ft |
| Occupants | +600 BTU per person beyond the first |
| Room Type | Kitchen: +4,000 BTU, Sunroom: +2,000 BTU, Basement: -10% |
| Insulation | Good: -10%, Poor: +10% |
| Sun Exposure | Shaded: -10%, Very Sunny: +10% |
| Windows | +200 BTU per window |
These calculations provide a reliable estimate for most residential applications. Final sizing should be confirmed by a qualified HVAC professional.
Common BTU Sizes
Here's a quick reference for common air conditioner BTU capacities and the room sizes they typically serve:
| BTU | Tonnage | Room Size (sq ft) |
|---|---|---|
| 5,000 | 0.42 | 150-250 |
| 6,000 | 0.5 | 200-300 |
| 8,000 | 0.67 | 300-350 |
| 10,000 | 0.83 | 350-400 |
| 12,000 | 1.0 | 400-550 |
| 18,000 | 1.5 | 600-900 |
| 24,000 | 2.0 | 900-1,200 |
Frequently Asked Questions
What is a BTU?
BTU stands for British Thermal Unit, a measurement of heat energy. One BTU is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. In air conditioning, BTU measures how much heat an AC unit can remove from a room per hour.
How many BTUs do I need per square foot?
As a general rule, you need about 20-25 BTUs per square foot of living space. However, this can vary based on ceiling height, insulation, sun exposure, room usage, and other factors. Our calculator accounts for all these variables to give you a more accurate estimate.
What is a "ton" in air conditioning?
In HVAC, a "ton" refers to the cooling capacity of an air conditioner. One ton equals 12,000 BTUs per hour, which is the amount of heat needed to melt one ton of ice in 24 hours. Residential AC units typically range from 1 to 5 tons.
Why is it bad to have an oversized AC unit?
An oversized AC will cool the room too quickly without running long enough to properly dehumidify the air. This results in a cold but clammy environment and can lead to mold growth. It also causes more frequent on/off cycling, which increases wear and energy costs.
What's the difference between this calculator and a Manual J calculation?
Our calculator provides a reliable estimate based on standard industry rules of thumb. A Manual J calculation is a more comprehensive method performed by HVAC professionals that considers additional factors like local climate, building materials, and specific window types and orientations.