AC Tonnage Calculator
Home & ConstructionFind the right air conditioner size for a room, and what it will cost to run each month.
Runs entirely in your browser — nothing is uploaded
Features
- Tonnage from room size, ceiling height, sun exposure and occupancy.
- Adjusts for a top floor with a roof above.
- BTU rating alongside the tonnage.
- Estimated monthly running cost at your tariff.
- Runs in your browser.
How to use the AC Tonnage Calculator
- 1Enter the room dimensions including the ceiling height.
- 2Set the sun exposure and how many people usually use the room.
- 3Read the recommended tonnage and the running cost.
Frequently asked questions
What size AC do I need for a 12 × 10 room?
A 120 sq ft room with a normal ceiling and moderate sun needs about 1 ton. Push to 1.5 tons if it is a top-floor room, takes heavy afternoon sun, or regularly holds more than three or four people.
Is a bigger AC better?
No — oversizing is a real mistake. An oversized unit cools the air quickly, switches off, and never runs long enough to remove humidity, leaving a room that is cold and clammy. It also cycles more, which wears the compressor and wastes energy.
Is an inverter AC worth the extra cost?
At more than about four hours of use a day, usually yes. An inverter compressor varies its speed instead of switching on and off, which cuts consumption substantially and holds the temperature more steadily. At light use the payback takes longer.