AC & Heat Pump BTU Calculator
Enter your room or building's square footage and a few basic details, and get an estimated BTU/hr cooling or heating load the starting point for equipment sizing.
- Covers All 8 Stocked Refrigerants
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- Updated for Current A2L Data
How the BTU Calculator Works
Three steps between you and a verified saturation reading no chart flipping required.
Enter square footage and ceiling height
The two biggest factors in total load, since more volume means more air to condition.
Add insulation, sun exposure, and occupancy
These adjust the base estimate up or down for real-world conditions.
Get your estimated BTU load
Use this number to size equipment or move on to the tonnage calculator.
How BTU Load Estimates Actually Work
A BTU estimate isn't just square footage times a fixed number climate, insulation, and sun exposure all shift the real load significantly.
Why a Flat Square-Footage Rule Falls Short
A commonly repeated shortcut 20 BTU per square foot ignores ceiling height, insulation, and climate entirely, and can be off by a significant margin for a poorly insulated space in a hot climate or an unusually well-insulated space in a mild one. This calculator factors in those variables instead of relying on one flat multiplier.
Cooling Load vs. Heating Load
Cooling and heating load aren't always the same number for a given space, since they respond differently to insulation, sun exposure, and climate. A heat pump sized purely on cooling load can end up undersized for heating in a cold climate, so both numbers matter for equipment selection.
From BTU Load to Equipment Tonnage
Once you have an estimated BTU load, the next step is converting it to equipment tonnage the industry-standard sizing unit for residential AC and heat pump equipment. The tonnage calculator on this site handles that conversion directly from your BTU result.
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Frequently Asked Questions
It's a rough starting point at best actual load depends heavily on insulation, ceiling height, sun exposure, and climate, all of which this calculator accounts for.
Whichever is larger for your climate in cold regions, heating load may exceed cooling load, and equipment should be sized to cover both needs.
Yes a room with 10-foot ceilings has roughly 25% more air volume to condition than the same footprint with 8-foot ceilings, which meaningfully changes the load.
Use the tonnage calculator to convert it into standard equipment sizing, typically rounding up to the nearest half-ton.
Need the Refrigerant to Match?
Every calculator links straight to the in-stock cylinder for that refrigerant.