BTU Calculator (AC Size)

What is the BTU Calculator (AC Size)?

Estimate air-conditioner capacity in BTU/h for a room. An air conditioner that is too small never cools the room, and one that is too large cycles on and off without removing humidity.

How to use the BTU Calculator (AC Size)

1. Enter your room area, your sun exposure, your regular occupants.
2. Tick the options you need: is a kitchen.
3. Results update automatically as you type; you can also press Calculate.
4. Read the output: recommended capacity, in tons, in kw.
5. Use the 📊 chart to see the result visually, then copy or share it.

Formula and method

Worked example

With room area = 400 ft², sun exposure = Normal, regular occupants = 2, is a kitchen = no, the BTU Calculator (AC Size) returns recommended capacity: 8,000 BTU/h; in tons: 0.67; in kw: 2.34.

Where the BTU Calculator (AC Size) helps in real life

You are buying a window unit for a 350 sq ft bedroom that gets afternoon sun. The calculator adjusts capacity for sunlight and occupants.

Your home office runs a computer and has two people working in it. Adding occupants shows why the room needs more cooling than its size alone suggests.

Common mistakes to avoid

• Using floor area only and ignoring sun exposure.
• Buying the largest unit available.
• Forgetting heat from kitchens or electronics.
• Ignoring poor insulation or high ceilings.

💡 Practical tip: An oversized air conditioner can leave a room cold but clammy because it shuts off before removing moisture.

Tips for better results

• Measure the room accurately.
• Adjust for sunny or shaded rooms.
• Check the unit’s energy efficiency rating.

⚠️ Material estimates are approximate. Follow local building codes and manufacturer instructions.

Related tools