AC & heating sizing guides
Short, practical guides to sizing the right air conditioner or heater — paired with the calculator that does the math.
What Size Air Conditioner for a 300 Square Foot Room?
A 300 sq ft room needs about 7,000 BTU of cooling from the EnergyStar chart — but sun, insulation, ceiling height, occupants, and kitchens all shift it. Here's how to size it right.
BTU Per Square Foot: How to Size a Room's AC or Heater
The rough rule is about 20 BTU per square foot for cooling and 30–60 for heating — but the EnergyStar chart and a few adjustments give a far more accurate room size. Here's the full picture.