BTU Calculator

Room Length (ft)

Optional if you provide total area.

Room Width (ft)

Optional if you provide total area.

Room Area (ft²)

If provided, overrides L×W.

Ceiling Height (ft)

Sizing scales with height vs 8 ft.

Occupants (people)

Beyond two: +600 BTU/h each.

Sun Exposure

Insulation

Windows (solar gain)

Climate

Special Use

Kitchen (+4,000 BTU/h)

Reset

Quick Conversions

Baseline: 25 BTU/h per ft² (rule-of-thumb for residential cooling).
Height: scales linearly vs 8 ft (height / 8).
Multipliers: exposure (−10%…+20%), insulation (−5%…+10%), windows (0…+15%), climate (−10%…+10%).
People: beyond two occupants, add 600 BTU/h each.
Kitchen: add 4,000 BTU/h for cooking/heat gains.
Conversions: 1 ton = 12,000 BTU/h, 1 W = 3.412141633 BTU/h, 1 kW = 3412.141633 BTU/h.
Disclaimer: This is a quick estimate. For permitting or major equipment, use ACCA Manual J or equivalent load calc.

Notes & edge cases

Large glazing, high internal gains (servers, aquariums), or extreme climates may require additional adders.
Results are rounded to the nearest 100 BTU/h for easier equipment selection.
If area is provided, length/width are ignored.