Cooling · Unit sizing
What size air conditioner do I need?
For a hot climate: room volume in cubic meters × 500 BTU/h, or × 600 with direct sun. A standard bedroom lands around 8,000–12,000 BTU/h (0.7–1 ton); a living room around 18,000–24,000 BTU/h. Enter your room below, then match the result to a unit size.
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
Match the result to a unit
Air conditioners come in standard capacities — pick the nearest size at or above your calculated load.
| Unit size (BTU/h) | Typically fits | Common form factor |
|---|---|---|
| 5,000 | Small bedroom, home office (shaded) | Window |
| 8,000 | Standard bedroom | Window / portable |
| 10,000 | Large bedroom, small living room | Window / portable |
| 12,000 | Living room, studio apartment | Mini-split / window |
| 18,000 | Large living room, open-plan area | Mini-split |
| 24,000 | Very large room, small open floor | Mini-split |
| 36,000 | Open floor plan, small shop | Mini-split / ducted |
Need the load itself explained? See the BTU calculator for the formula and room-size chart, or the tonnage calculator if your spec sheet is in tons.
FAQ
- What size air conditioner do I need for my room?
- Multiply the room's volume in cubic meters by 500 BTU (600 if it gets direct sun). A typical 12 × 15 ft room with an 8 ft ceiling needs about 20,000 BTU/h in a hot climate. Use the calculator above for your exact dimensions, then round up to the nearest available unit size.
- Should I round up or down to the nearest unit size?
- Round up when the room gets direct sun, has many occupants or appliances, or sits in a hot climate. Round down only when the room is shaded, well insulated, and in a mild climate — chronic oversizing causes short cycling and poor dehumidification.
- What happens if the AC is too small?
- An undersized unit runs continuously without reaching the set temperature, wears out faster, and drives up the power bill. If your result sits between two sizes in a hot climate, the larger unit is usually the safer choice.
- What happens if the AC is too big?
- An oversized unit cools the air quickly but shuts off before removing humidity, leaving the room cold and clammy. It also cycles on and off more, which increases wear and energy use.
- Does ceiling height matter?
- Yes. This calculator works from volume, not floor area, so a 12 ft ceiling raises the result by 50% compared with an 8 ft ceiling — something flat per-square-foot rules miss entirely.