Garage & Shop Heater BTU Calculator
Enter the size of the space and how well it is insulated to estimate heating capacity.
Last updated: May 2026
Buying and sizing notes
- Oversizing can cause short cycling. Undersizing may never bring the space up to temperature.
How to use this estimate
What this includes
- The required inputs shown on this page
- common planning assumptions
- optional advanced adjustments where provided
What it does not include
- site-specific professional design
- local code approval
- manufacturer-specific requirements
- installation quality
Common mistakes
- Leaving a required input at the default when your situation is different
- ignoring product labels or ratings
- treating the estimate as an exact final answer
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