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Garage Heater Size Calculator

Garage heater BTU from volume and temperature rise.

Inputs

Inputs and assumptions

Garage length.

Garage width.

Ceiling height.

Target indoor minus coldest outdoor temp in F. Rankine steps equal F steps; for C, multiply by 1.8.

Result

Heater size (BTU/hr)
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Electric equivalent (kW)
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What to check

  • Garage dimensions
  • Coldest outdoor temperature

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Rule-of-thumb screening estimate, not an ACCA Manual J calculation. Confirm with a room-by-room Manual J load calculation and installer quotes before buying equipment.

Saved calculations

Keep the assumptions with the result.

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