Cooling · BTU/h
BTU Calculator
A 12 × 15 ft room with an 8 ft ceiling needs roughly 20,400 BTU/h of cooling in a hot climate — about 1.7 tons. Enter your room's dimensions below to get the exact number in BTU/h, tons, kilowatts, and horsepower.
Room dimensions
- Tons
- 2.45 t
- Kilowatts
- 8.64 kW
- Horsepower
- 3.68 HP
- Room area
- 19.32 m²
- Room volume
- 58.9 m³
Cooling capacity
29,450BTU/h
≈ 2.45 tons · 8.64 kW
060,000
BTU by room size
Computed with the same formula as the calculator above (hot-climate volumetric method).
| Room | Area | BTU/h (shaded) | BTU/h (sunny) | Tons |
|---|---|---|---|---|
| 10 × 10 ft (8 ft ceiling) | 100 sq ft | 11,327 | 13,592 | 0.9 |
| 12 × 12 ft (8 ft ceiling) | 144 sq ft | 16,311 | 19,573 | 1.4 |
| 12 × 15 ft (8 ft ceiling) | 180 sq ft | 20,388 | 24,466 | 1.7 |
| 15 × 20 ft (8 ft ceiling) | 300 sq ft | 33,980 | 40,776 | 2.8 |
| 20 × 20 ft (9 ft ceiling) | 400 sq ft | 50,970 | 61,164 | 4.2 |
| 25 × 20 ft (9 ft ceiling) | 500 sq ft | 63,713 | 76,455 | 5.3 |
| 30 × 25 ft (9 ft ceiling) | 750 sq ft | 95,569 | 114,683 | 8 |
The formula
BTU/h = length(m) × width(m) × height(m) × factor
factor = 500 (shaded room)
factor = 600 (sun-exposed room)
tons = BTU/h ÷ 12,000
kW = tons × 3.52
HP = BTU/h ÷ 8,000Example: a 4 × 5 m room with 3 m ceilings, shaded — 60 m³ × 500 = 30,000 BTU/h, which is 2.5 tons or 8.8 kW.
FAQ
- How is this BTU number calculated?
- The calculator multiplies room volume by a load factor: BTU/h = length × width × height (in meters) × 500, or × 600 when the room gets direct sun. Because it uses volume instead of floor area, high ceilings correctly increase the result. Tons are BTU/h divided by 12,000.
- Why is the result higher than the 20 BTU per square foot rule?
- The 20 BTU/sq ft rule assumes a mild climate, standard 8 ft ceilings, and good insulation. This calculator uses a volumetric method (500–600 BTU/h per cubic meter) common in hot climates, where undersizing is the costlier mistake. Treat the result as a hot-climate estimate and the Energy Star chart as the mild-climate floor.
- What does the sun exposure toggle change?
- It raises the load factor from 500 to 600 BTU/h per cubic meter — a 20% increase. Use it when the room has large west- or south-facing windows or a sun-heated roof.
- How do I convert BTU to tons, kW, or HP?
- 1 ton of refrigeration = 12,000 BTU/h. Kilowatts are tons × 3.52, and horsepower is BTU/h divided by 8,000. The calculator shows all four so you can match any spec sheet.
- Is this a Manual J load calculation?
- No. This is a fast field estimate for guidance. A full ACCA Manual J accounts for insulation, windows, orientation, infiltration, and occupancy — use one for permits and final equipment selection on critical installs.