SettingsSettings for this calculationUS
The total floor area of the room to be heated.
Measure the room's length x width in the area to receive radiant floor heating.
The share of the room's floor area that will actually be covered by heating mat.
Heating mats are not installed under cabinets, vanities, tubs, or other fixed fixtures, so the usable coverage is always less than the full room area.
The heating mat product's rated power output per square meter.
Check the specific mat product's technical data sheet — rated output commonly falls in the 100-200 W/m² range. This figure is per SQUARE METER and stays exactly as typed when the room area above switches to square feet: it carries no unit of its own, so the toggle never touches it. A US data sheet rates the same mat per square foot, where this field's 100-200 W/m² range reads 9.3-18.6 W/sq ft — 1 W/m² is 0.0929 W/sq ft, so multiply a per-square-foot rating by 10.764 before entering it. Entered as it stands it falls under this field's minimum of 100 and the field rewrites it up to 100 on blur, reporting the substitution but not its cause: a mat rated 12 W/sq ft is 129 W/m², so the answer comes back 23% low — the direction that under-sizes the circuit and the thermostat. A rating given in Btu/h per sq ft is 3.155 W/m² each (1 W/m² = 0.317 Btu/h·ft²).
Total heating wattage
959 W
Confirm your specific mat product's rated output per square metre or square foot and your home's electrical circuit capacity before purchasing — radiant floor heating circuits typically require a dedicated GFCI-protected circuit.
- Heated mat area
- 68.8 sq ft
They open the calculator with your figures already in it
Heated Wire Floor Mat Coverage & Wattage Calculator: 959 W — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Heated mat area = room area × usable coverage fraction (excluding areas under cabinets/fixtures where mats aren't installed); total wattage = mat area × the mat product's rated watts per m² (commonly ~150 W/m²)
Inputs used
- Room Area
- 86 sq ft
- Usable Coverage (%, Excluding Fixed Cabinetry/Fixtures)
- 80
- Mat Rated Output (W per m²)
- 150
Intermediate steps
- Heated mat area
- 68.8 sq ft
Confidence note: Confirm your specific mat product's rated output per square metre or square foot and your home's electrical circuit capacity before purchasing — radiant floor heating circuits typically require a dedicated GFCI-protected circuit.
What this calculation does not cover
- Mats are not cut to fit. The heating wire cannot be cut anywhere along its length — only the mesh it is stapled to — so a floor is tiled out of standard factory mat sizes and the purchased area lands above the usable area computed here, sometimes well above in a room broken up by a vanity, a door swing and an angled wall. Lay the standard sizes onto the floor plan before ordering to the square meter.
- Wattage is not warmth. Whether this output holds a room at temperature depends on what sits above and below the mat: thick stone or porcelain responds far more slowly than vinyl or engineered timber, and without insulation board underneath, a large share of the output heats the slab rather than the room. At 150 W/m² over 80 percent of the floor this is a floor-warming figure — a room with big glazing or an exposed floor below often still needs another heat source to reach setpoint on a cold morning.
- The number has to fit the thermostat, not just the panel. A floor-heating thermostat typically switches around 15 or 16 A — roughly 1,800 W at 120 V and about 3,500 W at 230 V — so a floor above that needs two thermostats or a contactor, and each thermostat wants its own floor sensor run in the screed between wire runs rather than across one.
Add the equipment this sizes
This result is a specification — 959 W — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Part of a bigger job
Or plan the space itself: measure it once, doors and windows included, and this figure comes back worked out on that space, with what goes with it.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Heated mat area = room area × usable coverage fraction (excluding areas under cabinets/fixtures where mats aren't installed); total wattage = mat area × the mat product's rated watts per m² (commonly ~150 W/m²)
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