📏How long a baseboard heater does this room need?

✓ Tested & verified Updated: Aug 8, 2026 How we calculate this

Baseboard heater size calculator

Room length (ft)

Room width (ft)

Ceiling height (ft)

Insulation

1,750 W

The room works out at 1,680 W — 1,750 is the nearest size actually sold.

Floor area: 168 sq ft
Working rate: 10 W per sq ft
Baseboard length at 250 W per foot: 7 ft

Standard electric baseboard is 250 W per linear foot — so a 1,500 W room is six feet of heater, whether that is one length or two.

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How long should a baseboard heater be?

Work out the watts, then divide by 250. Electric baseboard puts out a standard 250 watts per linear foot, so a 14 × 12 ft bedroom needing 1,680 W takes about seven feet of heater — and that is the number to measure against the wall before ordering.

Ten watts per square foot is the same starting rate as any electric heat. What makes baseboard different is that the answer has to fit somewhere: seven feet of heater under a window is one 6 ft unit plus a short one, or two 4 ft units on different walls. Splitting the length across two walls is fine and often better, since baseboard works by convection and wants cold air falling onto it.

Put it under the window, not on the inside wall. The cold draught falls down the glass and the heater’s rising warm air meets it — that is the whole design. Furniture pushed against a baseboard heater stops the convection and is also a fire risk.

Baseboard is the one heater sized in feet, which makes it the one you can check against the wall before you buy. This is the conversion table.

Room	Watts	Feet of baseboard	Usual split
100 sq ft	1,000 W	4 ft	one 4 ft unit
150 sq ft	1,500 W	6 ft	one 6 ft unit
200 sq ft	2,000 W	8 ft	one 8 ft, or 2 × 4 ft
250 sq ft	2,500 W	10 ft	6 ft + 4 ft
300 sq ft	3,000 W	12 ft	2 × 6 ft

Measure the wall under each window before ordering. A room that calculates at twelve feet and has nine feet of clear wall needs a rethink — a taller-profile heater, a hydronic model, or accepting that this room wants a mini split instead.

Frequently asked questions

How many watts per foot is baseboard heat?

250 W per linear foot is the standard for residential electric baseboard, and almost every manufacturer builds to it: a 3 ft unit is 750 W, 4 ft is 1,000 W, 6 ft is 1,500 W and 8 ft is 2,000 W. A few premium and hydronic models run at 175 or 200 W per foot, which means a longer heater for the same output — check the label rather than assuming.

What circuit does a baseboard heater need?

Almost always a dedicated 240 V circuit: 1,500 W at 240 V is 6.25 amps, so a 20-amp circuit carries about 3,800 W of heater. Baseboard is a continuous load, so the circuit is loaded to 80% of its rating. Running baseboard on 120 V doubles the current for the same heat and is only done for small units.

Can I use two shorter heaters instead of one long one?

Yes, and it often works better. Total wattage is what heats the room; splitting it between two walls spreads the convection and copes better with a room that has glass on two sides. They can share a thermostat if they are on the same circuit and the thermostat is rated for the combined load.

Where should the thermostat go?

On an interior wall, about five feet up, away from the heater’s own rising air, away from direct sun and not above another heat source. A thermostat built into the heater itself is convenient and always reads warmer than the room, which is why the room ends up cooler than the dial says.

How far from the floor and the carpet?

Manufacturers specify a clearance — commonly at least three quarters of an inch above the floor covering — so air can enter underneath. A deep carpet fitted up to the heater blocks the intake, cuts the output and overheats the element. Curtains must clear the top by the stated distance too.

Is baseboard cheaper to run than a plug-in heater?

No. Every watt of electric resistance heat costs the same regardless of shape, and 1,500 W is 1,500 W. Baseboard’s advantages are that it is quiet, hard-wired so it is not limited to 1,500 W, thermostatically controlled per room, and out of the way. Cheaper running means a heat pump, not a different resistance heater.

How we calculate this

Wattage uses 10 watts per square foot of floor at an eight-foot ceiling, scaled by ceiling height ÷ 8 and corrected for insulation (+15% poor, −10% good) — the same basis as any electric resistance heating. The result rounds up to the wattages baseboard units are built in and is then divided by 250 watts per linear foot, the residential standard, to give a length. Low density models at 175 or 200 W per foot need proportionally more length for the same output. Circuit figures follow the continuous-load rule of 80% of the breaker rating.

Worked example

With Room length (ft) 14, Room width (ft) 12, Ceiling height (ft) 8, Insulation Average — typical home, this page works out 1,750 W. The room works out at 1,680 W — 1,750 is the nearest size actually sold.

Floor area168 sq ft
Working rate10 W per sq ft
Baseboard length at 250 W per foot7 ft

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