Heat Pump Sizing Calculator
Estimate heat pump capacity in BTUs and tons by area and climate.
Enter the square footage you're conditioning and your climate to estimate heat pump capacity in BTUs per hour and tons. This is a quick guide — a Manual J load calculation is the right way to size for a purchase, especially in cold climates where backup heat matters.
How it works
Capacity scales with area and climate. As a rough guide, allow about 25 BTU per square foot in mild climates, 30 in moderate ones, and 40 in cold ones. Divide the total by 12,000 to get tons. Cold-climate systems often pair a heat pump with supplemental heat.
Frequently asked questions
What size heat pump do I need?
Multiply your area by a climate factor — about 25 BTU/sq ft in mild climates, 30 in moderate, 40 in cold. A 1,200 sq ft home in a moderate climate needs roughly 36,000 BTU, or 3 tons.
How many BTUs is a ton of heat pump capacity?
One ton equals 12,000 BTU per hour, the same as for air conditioning.
Do heat pumps work in cold climates?
Modern cold-climate heat pumps do, but they're usually paired with supplemental electric or gas heat for the coldest days. Size with a Manual J calculation.
Is this calculator free and private?
Yes. Every CubicCabin calculator runs entirely in your browser, so the numbers you enter are never uploaded or stored. There's no sign-up, no limits, and it keeps working even if you lose connection after the page loads.