HVAC
HVAC Tonnage Calculator
Convert a home's size and climate into the cooling tonnage an HVAC system needs.
Result
A rule-of-thumb estimate for early conversations. Equipment should be selected on a room-by-room load calculation (ACCA Manual J) and the ducts designed to match (Manual D). Oversized equipment short-cycles, dehumidifies poorly and wears out early, so guessing high is not the safe option it looks like.
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About this calculator
How many square feet per ton is right?
Between about 400 and 700 depending on climate and how well the house is built. A tight new home in a mild climate needs far less equipment than the same floor area built in 1965.
Is a bigger unit safer?
No. An oversized system cools the air fast, shuts off before it has removed the humidity, and short-cycles. The house feels cold and clammy and the compressor fails early.
Does this replace a Manual J?
No. Manual J models each room's windows, orientation, insulation and air leakage. This is a sanity check before that work is done, not a substitute for it.
The formula
BTU = area x climate factor x envelope adjustment + occupant load; tons = BTU / 12,000
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