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Calcimator

BTU Calculator

Calculate heating and cooling BTU requirements for your room or home. Determine the right AC tonnage and furnace size based on room dimensions, insulation, and climate.

Inputs

ft
ft
ft
sq ft

Results

Cooling Capacity Needed

10,000 BTU/hr

Heating Capacity Needed22,000 BTU/hr
AC Tonnage1 tons
Recommended Cooling UnitWindow unit or mini-split (9,000-12,000 BTU)
Recommended Furnace40,000 BTU furnace
Room Area300 sq ft
How to Use This Calculator
  1. Enter the room length, width, and ceiling height in feet.
  2. Select the ceiling type (standard, high, or vaulted) and insulation quality.
  3. Choose your climate zone and sun exposure to adjust the load estimate.
  4. Enter the total window area in square feet — more glass increases both heating and cooling loads.
  5. Read the cooling BTU/hr and AC tonnage to size an air conditioner, and heating BTU/hr to size a furnace.
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