Free BTU Calculator

Estimate the BTU rating needed to heat or cool a room.

This is a rule-of-thumb estimate (roughly 20 BTU per sq ft as a baseline for cooling), not a full Manual J load calculation — for whole-home HVAC sizing, insulation quality, window count, climate zone, and other factors matter significantly and a professional load calculation is recommended.

Worked Example

Example: A 300 sq ft room with standard 8ft ceilings and average sun exposure needs approximately 6,000 BTU for cooling.

Formula / Method

BTU ≈ Square Footage × 20, adjusted ±10% for high sun exposure or shade, and scaled for ceiling height above 8ft.

Worked Example

Example: A 300 sq ft room with standard 8ft ceilings and average sun exposure needs approximately 6,000 BTU for cooling.

Formula / Method

BTU ≈ Square Footage × 20, adjusted ±10% for high sun exposure or shade, and scaled for ceiling height above 8ft.