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Redmoon Converters
🔨 Construction & DIY

BTU & HVAC Sizing Calculator

Size an AC, heat pump or heater for any room using a Manual-J-lite heuristic: area, ceiling height, insulation, climate zone, sun exposure and occupants.

sqft
ft
+600 BTU each.
Recommended capacity
0 BTU/hr
0 tons · 0 kW
ComponentBTU/hr
How the math works

Manual-J-lite heuristic: base 20 BTU/sqft × area × insulation × climate × sun, scaled by ceiling height (relative to 8 ft / 2.4 m).

Then add 600 BTU per occupant and +4000 BTU if the space is a kitchen (appliance load).

Tonnage: 1 ton of cooling = 12 000 BTU/hr. kW (heat pump output): BTU/hr ÷ 3412.

For final sizing always confirm with a Manual-J load calculation done by a qualified HVAC contractor — this tool is for first-pass sizing only.

Also known as

btu calculatorair conditioner size calculatorac btu calculatorheat pump size

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