Air Conditioner Size Calculator
BTU capacity for a room.
Enter your values
Enter the room area in sq ft.
Enter the ceiling height in ft.
Enter the regular occupants you are working with.
Choose one of: Very shady, Average, Very sunny.
Choose one of: No, Yes.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Required capacity
- 6,000 BTU/h
- In tons
- 0.5
- Typical unit to buy
- 1 ton
- Estimated running watts
- 600
- Room area
- 300 sq ft
Quick answer
Start from 20 BTU per square foot, then adjust for sunlight, ceiling height, kitchens and extra occupants.
BTU = area × 20 + adjustments
At a glance
| What it does | BTU capacity for a room. |
|---|---|
| Category | Home & DIY |
| Inputs needed | Room area, Ceiling height, Regular occupants, Sun exposure, Is it a kitchen? |
| Main output | Required capacity |
| Formula | BTU = area × 20 + adjustments |
| Cost | Free — no sign-up, no download |
How to use the Air Conditioner Size Calculator
- 1Measure the room's floor area in square feet.
- 2Enter ceiling height and occupancy.
- 3Adjust for sun exposure and kitchen heat.
Inputs explained
- Room area(sq ft)
- Enter the room area in sq ft.
- Ceiling height(ft)
- Enter the ceiling height in ft.
- Regular occupants
- Enter the regular occupants you are working with.
- Sun exposure
- Choose one of: Very shady, Average, Very sunny.
- Is it a kitchen?
- Choose one of: No, Yes.
Worked example
Using the values the calculator loads with:
Inputs
- Room area300 sq ft
- Ceiling height8 ft
- Regular occupants2
- Sun exposureAverage
- Is it a kitchen?No
Results
- Required capacity6,000 BTU/h
- In tons0.5
- Typical unit to buy1 ton
- Estimated running watts600
- Room area300 sq ft
Frequently asked questions
Is bigger better?
No — an oversized unit short cycles and leaves the room humid.
What about insulation?
Poorly insulated rooms need 10–20% more capacity.
What do I need to enter into the Air Conditioner Size Calculator?
Just 5 values: room area, ceiling height, regular occupants, sun exposure, is it a kitchen?. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Air Conditioner Size Calculator work out the answer?
Start from 20 BTU per square foot, then adjust for sunlight, ceiling height, kitchens and extra occupants. It applies the formula BTU = area × 20 + adjustments and shows the working so you can check each step by hand.
Is the Air Conditioner Size Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.