AC BTU Calculator

Find how many BTU you need for air conditioning, based on the room area and sun exposure, plus the recommended unit size.

Enter your data

Room area

m²

Sun exposure

Enter the room area and choose the sun exposure. The result shows the AC unit size that fits.

=BTU needed

9,810BTU

Cooling power2,875 W

Equivalent2.9 kW

Recommended unit12,000 BTU

Indicative estimate (~100–135 W/m² for a 2.6 m ceiling). Increase for kitchens, top-floor rooms, large south-facing windows and crowded rooms.

Handy everyday tools. Simple, fast calculations for common situations. Everything runs instantly in your browser, no account, no data sent.

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iHow it is calculated

The requirement comes from the area and the cooling power per m², converted to BTU (× 3.412):

BTU = area × W/m² × 3.412

For a normal 25 m² room (≈115 W/m²): 25 × 115 × 3.412 ≈ 9,810 BTU, so a 12,000 BTU unit.

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How many BTU do I need for a room?

About 100–135 W per square metre, converted to BTU (× 3.412). For a normal 25 m² room that is around 9,500 BTU, so a 12,000 BTU unit.

How is the BTU requirement for air conditioning calculated?

Multiply the room area by the cooling power per square metre (≈115 W/m² for a normal room) and convert watts to BTU by multiplying by 3.412.

How many BTU for 20, 30 or 50 m²?

Roughly: ~9,000 BTU for 20 m², ~12,000 BTU for 30 m² and ~18,000–24,000 BTU for 50 m². Adjust for exposure and insulation.

What does BTU mean on an air conditioner?

BTU (British Thermal Unit) per hour is the unit that measures cooling power. The higher the value, the larger the room the unit can cool.

Which AC unit should I choose for my room?

Pick the smallest standard size (9,000, 12,000, 18,000, 24,000 BTU) that covers the calculated need. Slightly larger is fine, far too large is not.

Is it a problem if the unit is too big?

Yes. An oversized unit cools too fast, switches on and off often (short cycling), dehumidifies poorly and uses more energy, wearing out faster.

What factors increase the BTU requirement?

Sun exposure, large windows, the top floor or attic, the kitchen, the number of people and electronics. All add heat and raise the power needed.

Do BTU affect energy consumption?

The cooling power (BTU) and efficiency (SEER) determine consumption. A correctly sized unit with a high SEER and good energy class uses the least.

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