BTU / HVAC Sizing Calculator
Estimate the cooling capacity (BTU/hr) needed to air-condition a room. Adjusts for sun exposure, insulation, and occupancy.
Inputs
BTU/hr needed
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Recommended size (next up)
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In tons (central AC)
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Floor area
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About BTU / HVAC Sizing Calculator
BTU basics
BTU = British Thermal Unit. AC capacity is in BTU per hour (BTU/hr). Common rule: 20 BTU per sq ft of floor space for moderate climates, more for very hot/sunny rooms or insulated spaces.
Don’t oversize
A too-large AC cools quickly then shuts off, never running long enough to dehumidify. Result: cold but clammy room. Slightly undersized + longer run cycles is usually better than oversized.
Heat pumps and central AC
Central AC is sized in tons (1 ton = 12,000 BTU/hr). A typical 1,500-2,000 sq ft home needs 2-3 tons of cooling. Heat pumps in cold climates may need supplemental heat — local HVAC pros do load calculations (Manual J) for accurate sizing.