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Home & Basement

Mini Split BTU Calculator

Enter room size and conditions to estimate a starting BTU or kW range for a mini split. This is not a Manual J load calculation.

Last updated: May 2026

Unit system Switch between U.S. customary and metric units. Your choice is remembered on other calculators.

Room details

Enter the room area using the unit selector. Adjust the modifiers if the room is sunny, poorly insulated, or has high ceilings.

sq ft
Advanced settings
BTU/sq ft
A rough planning factor only. Use lower for mild/well-insulated rooms and higher for difficult rooms.
%
Increase for poor insulation, high sun, high ceilings, or colder/hotter climates.

Buying and sizing notes

How to use this estimate

What this includes

  • Room area
  • base BTU per square foot
  • adjustment factor
  • BTU/hr and kW equivalent

What it does not include

  • Manual J load calculation
  • duct losses
  • solar gain details
  • local climate design conditions

Common mistakes

  • Oversizing for the space
  • Ignoring insulation and air sealing
  • Using area only for a complicated layout

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