Workshop Heating (BTU) Calculator
Size a garage or workshop heater based on your space, insulation, and climate.
BTU needed
How this calculator works
Garage heating load scales with floor area, ceiling height (more air volume to heat), insulation quality, and how cold your climate gets. This calculator uses a base BTU-per-square-foot figure that varies by insulation level, adjusts for ceiling height above the standard 8 ft assumption, and applies a climate multiplier.
Where these numbers come from
Base BTU-per-square-foot figures reflect typical garage heating guidance from heater manufacturers, adjusted for insulation quality. Garage doors are a major, often-underestimated heat loss source -- an insulated garage door meaningfully lowers real-world heating needs versus an uninsulated one, which this calculator accounts for through the insulation-level selection.
Frequently asked questions
Does the garage door really matter that much?
Yes -- an uninsulated garage door is one of the largest heat-loss surfaces in most garages, often larger than any single wall, which is why insulation level (including the door) significantly changes the BTU estimate here.
Should I size for the coldest day or the average winter day?
Size for close to your coldest realistic day, not the average -- undersizing means the heater can't keep up exactly when you need it most, on the coldest days.
What heater types deliver this many BTU?
Common garage heater options include electric infrared, propane forced-air, and natural gas forced-air units, each rated in BTU/hr by the manufacturer -- match your calculated need to a unit's rated output.
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