BTU calculator
Work out roughly what size air conditioner a room needs. It takes under a minute, and you can send the result straight to us for a quote.
Estimate: 7 800 BTU per hour. Closest standard size 9 000 BTU.
Estimated cooling needed
About 2.3 kW for 20 m²
A 9 000 BTU unit is the closest standard size.
Your room details go with the request, so we can check the size before quoting. This is a rule-of-thumb estimate: insulation, windows, appliances and use all change the real load, so we confirm on site.
Typical unit sizes
A rough guide for a standard 2.4–2.7 m ceiling with average sun. Sunny rooms, kitchens and rooms under the roof need more. How we size and install units.
| Unit size | Room area | Typical use |
|---|---|---|
| 9 000 BTU | Up to about 15–20 m²Small bedrooms and studies | Small bedrooms and studies |
| 12 000 BTU | About 20–30 m²Main bedrooms, small lounges and offices | Main bedrooms, small lounges and offices |
| 18 000 BTU | About 30–45 m²Lounges, open-plan living and larger offices | Lounges, open-plan living and larger offices |
| 24 000 BTU | About 45–60 m²Large living areas and small shops | Large living areas and small shops |
| 30 000 BTU and up | 60 m² and moreShops, restaurants and open-plan offices; often cassette or ducted | Shops, restaurants and open-plan offices; often cassette or ducted |
About BTU sizing
What does BTU mean?
BTU stands for British Thermal Unit. For air conditioners it is used as BTU per hour: how much heat the unit can remove from a room in an hour. 12 000 BTU/h is about 3.5 kW of cooling.
Is a bigger air conditioner better?
No. An oversized unit cools the room quickly and then switches off before it has removed the moisture, which leaves the room cold but clammy, and it cycles on and off more, which wears it out. The right size runs longer, more gently and more efficiently.
How accurate is this calculator?
It is a rule-of-thumb estimate and a good starting point. Insulation, window size and direction, appliances and how the room is used all affect the real cooling load, so we always confirm the size on site before quoting.
Got your number? Let's confirm it on site.
Send a few details and we will come back to you with next steps, or call and speak to a director directly.