Baseboard Heater BTU Calculator
BTU and length of electric baseboard heater needed.
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ⓘ Live results
Results
- Heater wattage needed
- 1,500 W
- Heat output
- 5,118 BTU/hr
- Baseboard length needed
- 6 ft
Quick answer
Baseboard heaters are commonly sized at 10 watts per square foot, then converted to BTU and physical heater length.
watts = area x 10; BTU = watts x 3.412; length = watts / watts per foot
How to use the Baseboard Heater BTU Calculator
- 1Measure the room floor area.
- 2Use about 10 W per sq ft for average insulation, more for poorly insulated or high-ceiling rooms.
- 3Divide total wattage by the heater's output per foot (commonly 250 W/ft) to get the length needed.
Worked example
Using the values the calculator loads with:
Inputs
- Room area150 sq ft
- Sizing rate10 W/sq ft
- Heater output250 W/ft
Results
- Heater wattage needed1,500 W
- Heat output5,118 BTU/hr
- Baseboard length needed6 ft
Frequently asked questions
Should I split the heater into two units?
Yes, placing heaters under two windows or on two walls improves comfort versus one long unit.
Does ceiling height matter?
Yes, rooms over 8 ft ceilings need extra wattage — add roughly 10% per additional foot.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.