Refrigerant BTU Calculator

Multiply the space's volume in cubic feet by 0.24 (the specific heat of air, in BTU per pound per °F) by the temperature difference between the outside air and the inside holding temperature. Volume × 0.24 × Temperature Difference gives you a quick estimate of the cooling capacity in BTU per hour.

A BTU, or British Thermal Unit, is the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit. In cooling and refrigeration it measures the amount of heat removed per hour, sometimes written as BTUH (BTU per hour).

It depends on the size of the box and the temperatures involved, so use the calculator for your specific case. As a rough sense of scale, a small walk-in cooler might need a few thousand BTU per hour, while a large cooler or freezer can need far more. Always confirm with a full load calculation before buying equipment.

A freezer holds a much lower inside temperature than a cooler, so the temperature difference between the room and the box is larger. A larger temperature difference means a higher BTU load, which is why freezers generally need more cooling capacity than coolers of the same size.

Yes. This calculator gives a base air-cooling estimate only. Warm incoming product, frequent door traffic, lights, evaporator fans, and people working inside all add heat load on top of the base figure. Add a safety margin and run a full load calculation to account for them.

One ton of refrigeration equals 12,000 BTU per hour, so divide your BTU figure by 12,000 to get tons. For example, 24,000 BTU/hr is 2 tons of refrigeration. The calculator shows tons automatically.

The specific heat of air is about 0.24 BTU per pound per °F — the amount of heat needed to raise one pound of air by one degree Fahrenheit. That 0.24 value is the constant used in the formula on this page.

No. It's a quick field estimate based on cooling the air in the space. It does not account for product load, door openings, insulation, or equipment heat. Refine it with a full refrigeration load calculation before final sizing.

Yes, it's completely free with no signup required. Your inputs are saved locally in your browser so they persist between visits, and nothing is uploaded to a server.