Estimate the cooling capacity a room needs to stay comfortable in the summer.
Room Area (sq ft) — Engineering quantity in sq ft. Influences the result through the governing physical formula; check units. Example: 250 sq ft.
Typical Occupants — Engineering quantity. Influences the result through the governing physical formula; check units. Example: 2.
Sun Exposure — Engineering quantity. Influences the result through the governing physical formula; check units. Example: moderate.
Recommended Capacity
6,510 BTU/hr
Recommended Capacity — Calculated outcome BTU/hr. Derived from your inputs via the displayed formula; use to plan.
In Tons (12,000 BTU/hr)
0.54
In Tons (12,000 BTU/hr) — Calculated outcome. Derived from your inputs via the displayed formula; use to plan.
Base Load (Area)
5,000 BTU/hr
Base Load (Area) — Calculated outcome BTU/hr. Derived from your inputs via the displayed formula; use to plan.
Occupant Load
1,200 BTU/hr
Occupant Load — Calculated outcome BTU/hr. Derived from your inputs via the displayed formula; use to plan.
Sun Adjustment
5%
Sun Adjustment — Percentage %. Above 0 increases with input; compare to benchmarks or goals.
What this means
Start with a base 20 BTU/hr per square foot of area, add 600 BTU/hr per occupant, then scale the subtotal by the sun-exposure factor. The result is an estimate for typical 8-foot ceilings and average insulation — not a substitute for a Manual J load calculation.
A cooling load is the heat an air conditioner must remove to keep a room comfortable. This tool applies a published rule-of-thumb based on area, occupants, and sun exposure to estimate the needed capacity in BTU/hr.
Formula
BTU/hr ≈ (area × 20) + (occupants × 600), then adjusted for sun exposure (+5% moderate, +10% significant)
Worked examples
FAQ
Is this the same as a Manual J load calculation?
No. This is a screening rule of thumb. A Manual J calculation by a professional accounts for window glazing, insulation levels, ceiling height, and house-specific details.
Should I size slightly larger than the estimate?
Slightly oversizing is common, but heavily oversized units short-cycle, dehumidify poorly, and waste energy. Treat the estimate as a starting point.