Sizing & Load
Work out what size AC, furnace, heat pump or mini-split a home needs — cooling and heating BTU and tonnage from floor area, a climate-zone rule-of-thumb band and adjustments, plus ton/BTU/kW conversion and airflow. Rule-of-thumb sizing is a starting estimate, not a Manual J.
Sizing accuracy: Rule-of-thumb sizing is a starting estimate, not a substitute for a professional Manual J / Manual S load calculation. Bigger is not better — an oversized system short-cycles, controls humidity poorly and wastes energy. Have a pro run a load calc before buying equipment.
AC SizeEstimate the AC size your home needs in BTU/h and tons from square footage, climate zone, sun, occupancy and ceiling height. Free, no signup.Furnace SizeEstimate the furnace size your home needs: heating output BTU from area and climate, then input (firing) BTU from AFUE efficiency. Free, no signup.Heat-Pump SizeEstimate the heat pump size your home needs in tons and BTU/h from area, climate, sun, occupancy and ceiling — with a capacity-derating note. Free.Mini-Split / Room BTUEstimate the BTU a single room or mini-split zone needs from its area, sun, occupancy and ceiling — using the EPA 20 BTU/sq ft room guideline. Free.Tons ↔ BTU ↔ kWConvert cooling capacity between tons, BTU per hour and kilowatts, and see the implied airflow. 1 ton = 12,000 BTU/h = 3.517 kW. Free, instant.Airflow (CFM) from TonsEstimate the airflow in CFM an HVAC system moves from its tonnage, at the standard 400 CFM per ton (350–450 range). Free, instant, no signup.
Every Sizing & Load tool is calculated server-side — visible immediately — with its formula, a worked example and a reference table. Background reading is in the guides.