Project estimates

BTU Calculator

Calculate the BTU (British Thermal Units) needed to heat or cool a room based on size, insulation, and climate. Use this Construction and home tool to enter your numbers, review the result, and understand the key assumptions before making the next decision.

What you get
A focused calculator, clear explanation, common questions, and useful next tools.
Quick intro
Calculator
Result
Explanation
Common questions
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How this calculator works
The result depends on the numbers you enter and the assumptions shown below.

A general rule: 20 BTU per square foot for cooling. Adjust for: high ceilings (+15%), sunny rooms (+10%), heavy shade (−10%), occupants (+600 BTU each beyond 2). Heating needs vary more by climate.

Review the inputs carefully and treat the output as an estimate. For decisions involving money, taxes, health, law, or security, compare the result with trusted professional guidance when needed.

Frequently asked questions

What does BTU stand for?

BTU stands for British Thermal Unit — the amount of energy needed to raise 1 pound of water by 1°F. For HVAC, higher BTU = more heating/cooling power.