Air Conditioner Size Calculator

Find the right size air conditioner for a room.

BTU NEEDED
BTU
cooling

Usage Tip

Too big means short cycling and humidity problems. About 1 ton per 400 sq ft is a rough guide.

THE MATH
BTU = Area × 25 × sun × kitchen
Where: 25 BTU per sq ft base  •  sun 0.9-1.1  •  kitchen +25%
• Tons = BTU ÷ 12,000
• Buy the next size up in 6,000 BTU steps
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The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.