Electric baseboard watts from BTU per hour
The baseboard tab divides a room load by 3.41. It does not use a watts-per-square-foot chart.
The conversion
baseboardWatts divides BTU/hr by 3.41 and returns watts. DOE’s forced-air guide divides Btu/h by 3,412 and returns kilowatts. The two divisors are this calculator’s 3.41 and DOE’s 3,412. Neither divisor is a watts-per-square-foot rule.
Placement
Baseboard works by convection along the surface it is mounted on. Put it on an exterior wall, ideally under a window, and keep towel bars and curtains off it. Circuit sizing, wire, and the breaker belong to a licensed electrician. This page does not pick a breaker.
120 V and 240 V
Amps = watts ÷ volts. The same wattage draws twice the current at 120 V that it draws at 240 V, because the voltage is half. Thermostats for baseboard are line-voltage. This page does not print a maximum wattage for a breaker.
As an Amazon Associate I earn from qualifying purchases. The Amazon links below are affiliate links; they don't change the math.
Once you've sized the room: standard 240 V baseboard heaters by wattage class, line-voltage smart thermostats (Mysa-style) that schedule rooms down when empty, and heater covers that look better than the originals. baseboard heaters on Amazon · line-voltage thermostats on Amazon · heater covers on Amazon
Need an electrician for the circuit work?
Run your exact room in the baseboard watts calculator.
Furnace and heat-pump strip coils use the same kind of conversion, with DOE's 3,412 Btu/h per kW set next to this page's ÷ 3.41: BTU to kW.
Sources & Standards
Related standards. These pages describe the publications and do not print the rule-of-thumb factors used in the calculators: