Free HVAC BTU Calculator

Calculate the BTU capacity needed for heating or cooling a room based on square footage and conditions.

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sq ft
ft

Recommended BTU

6,000

AC Tonnage0.5

Recommended BTU vs Room Size

View formula & how it works →

BTU Calculation

Base BTU = Square Footage × 20

Adjustments:

  • High ceilings: +5% per foot above 8ft
  • Sun exposure: ±10%
  • Extra occupants: +600 BTU each beyond 2
  • Kitchen: add 4,000 BTU

    • 1 ton of AC = 12,000 BTU

    Example Calculation

    300 sq ft room, 8ft ceiling, average sun, 2 occupants.

    1. 01Base BTU = 300 × 20 = 6,000
    2. 02Ceiling factor = 1.0 (standard height)
    3. 03Sun factor = 1.0 (average)
    4. 04Occupant BTU = 0 (2 is baseline)
    5. 05Total = 6,000 BTU
    6. 06Tonnage = 6,000 / 12,000 = 0.5 ton

    Frequently Asked Questions

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