Sizing

Manual J Load Calculator

Answer seven quick questions and get a realistic heating and cooling load estimate for your space — the same factors a pro considers, simplified for shortlisting the right system.

Tell us about the space

The space this system will heat and cool
Where the home is
Rough guide by home age
1 = one open space or one room

What is a Manual J calculation?

Manual J is the industry-standard method (from ACCA) for working out how much heating and cooling a home actually needs. Instead of guessing from square footage alone, it accounts for climate, insulation, ceiling height, windows, sun, and the people inside — because an oversized system short-cycles and dehumidifies poorly, while an undersized one runs nonstop and still falls behind on the hottest and coldest days.

How this calculator works

This tool runs a simplified block-load version of that method: it starts from climate-based load factors and adjusts for your ceiling height, insulation level, window exposure, kitchen heat, and occupancy. The result is a realistic sizing range for shortlisting equipment — most homes land squarely on one standard system size.

When to get a full Manual J

For new construction, additions, homes with unusual layouts, or utility rebate paperwork that requires documentation, a room-by-room Manual J from a pro is worth it. Our team does free sizing checks on every order — send us your numbers and we’ll confirm the right fit before anything ships.