Radiant Heat Layout Calculator: How to Determine Heated Area

Understanding Radiant Floor Heat

Traditional electric radiant floor heating mats and cables, like those made by SunTouch, Warmup, Nuheat, and Schluter-Systems, are resistance heating systems. This means the wire in each size of the heating element is individually designed to ensure it puts out the optimal amount of heat. This also means that cutting the element shorter or splicing more material on to lengthen it will cause the element to heat improperly and could potentially lower the life span of the system, so it’s especially important to ensure that you order the right amount of mats or cables to best fit your area. If that sounds complicated, don’t worry, we’re here to help!

Learn more about radiant floor heating.

Calculating Heated Floor Area

The best way to determine what size mat or cable you need is to create a dimensioned drawing of the room. Your drawing doesn’t have to be pretty, but it does need to be accurate. Include accurate measurements of walls and built-in fixtures such as vanities and kitchen islands, and note the location of any vents or drains. For bathrooms, also include a measurement from the wall behind the toilet to the flange or base of the toilet. You won’t be heating underneath built-in vanities, bathtubs, etc. You’ll use the drawing to calculate the total heated area square footage.

To learn more about measuring for specific products, scroll toward the bottom of this article.

Below is a helpful tool to help you measure. We’ll be using a bathroom as an example.

Now that you’ve measured your space and sketched in all the items that need to be marked on the floor plan, here are a few additional questions we want you to think through.

Full Coverage or spotheat?

We recommend you heat any part of the floor where you will walk or stand. But you can choose to only spotheat the floor where you stand most often. (We’ve never gotten a complaint from anyone who’s covered the full floor, but some people do say they wish they had NOT done the spotheat method.) Here’s what we mean:

Spot coverage

Spot coverage

Full Coverage

Full Coverage

How Much Mat or Cable Do You Need?

Next, the process for determining which mat or cable you need depends on the product being installed. Find the product you plan on installing to learn measuring specifics.

Nuheat Standard Mats

Start by calculating the square footage of the room's open area(s) (anything not covered by built-in fixtures or obstructed by vents or drains), commonly referred to as the “tiled area” of the room.

Select a mat or assortment from the Nuheat Standard Mat section that best fits the tiled area without getting closer than 6 inches to the toilet flange and 2 inches from walls with baseboards.

NOTE: Nuheat mats cannot be cut or shaped, so if there is not a mat that fits the area, choose the next size down.

Shop Nuheat Mats

Nuheat Cable

Start by calculating the square footage of the open area(s) (anything not covered by built-in fixtures or obstructed by vents or drains), commonly referred to as the “tiled area” of the room.

NOTE: Nuheat cables are safe (UL listed) for installation in showers, but it is recommended to use a separate mat or cable in the shower, so calculate the main area and the shower separately when heating a bathroom.

While the cables can be installed close to toe kicks, tubs, cabinets, and showers, they should be 2-4 inches away from the walls. To make sure you will have an adequate border, multiply the total tiled area by 0.9 to figure out the total heated area.3

For bathrooms, subtract from the tiled area a section around the toilet flange large enough to keep the heating elements 6 inches away from the wax ring (usually 2-4 square feet).

Finally, select the length of cable (or cables) that covers the square footage closest to your heated area. Remember, you can connect up to three cables to one thermostat so long as the combined amperage is less than 15.

Shop Nuheat Cable

DITRA-HEAT

Start by calculating the total square footage of the room, including under built-in fixtures such as cabinets, kitchen islands, and vanities. While you will not be heating this entire area, you will need to cover it with the DITRA-HEAT membrane, so keep this number handy.

Next, calculate the square footage of the open area(s) (anything not covered by built-in fixtures or obstructed by vents or drains), commonly referred to as the “tiled area” of the room.

NOTE: DITRA-HEAT cables are safe (UL listed) for installation in showers, but it is recommended to use a separate mat or cable in the shower, so calculate the main area and the shower separately when heating a bathroom.

While the cables can be installed close to toe kicks, tubs, cabinets, and showers, they should be 3-4 inches away from the walls. To make sure you will have an adequate border, multiply the total tiled area by 0.9 to figure out the total heated area.

For bathrooms, subtract from the tiled area a section around the toilet flange large enough to keep the heating elements 6 inches away from the wax ring (usually 2-4 square feet).

Finally, select the length of cable (or cables) that covers the square footage closest to your heated area. Remember, you can connect up to three cables to one thermostat so long as the combined amperage is less than 15.

Shop DITRA-HEAT

SunTouch Mats

Start by calculating the square footage of the open area (anything not covered by built-in fixtures or obstructed by vents or drains), commonly referred to as the “tiled area” of the room.

NOTE: SunTouch mats are safe (UL listed) for installation in showers, but it is recommended to use a separate mat or cable in the shower, so calculate the main area and the shower separately when heating a bathroom.

While the mats can be installed close to toe kicks, tubs, cabinets, and showers, they should be 2-4 inches away from the walls. To make sure you will have an adequate border, multiply the total tiled area by 0.9 to figure out the total heated area.

For bathrooms, subtract from the tiled area a section around the toilet flange large enough to keep the heating elements 6 inches away from the wax ring (usually 2-4 square feet).

Finally, select the right size mat (or mats) to cover the square footage closest to your heated area. Remember, you can connect up to three mats to one thermostat so long as the combined amperage is less than 15.

Shop SunTouch Mats

Warmup Cables

Start by calculating the square footage of the open area(s) (anything not covered by built-in fixtures or obstructed by vents or drains), commonly referred to as the “tiled area” of the room.

NOTE: Warmup cables are safe (UL listed) for installation in showers, but it is recommended to use a separate mat or cable in the shower, so calculate the main area and the shower separately when heating a bathroom.

While the cables can be installed close to toe kicks, tubs, cabinets, and showers, they should be 2-4 inches away from the walls. To make sure you will have an adequate border, multiply the total tiled area by 0.9 to figure out the total heated area.

For bathrooms, subtract from the tiled area a section around the toilet flange large enough to keep the heating elements 6 inches away from the wax ring (usually 2-4 square feet).

Finally, select the length of cable (or cables) that covers the square footage closest to your heated area. Remember, you can connect up to three cables to one thermostat so long as the combined amperage is less than 15.

Shop Warmup Cables

Warmup Sticky Mats

Start by calculating the square footage of the open area(s) (anything not covered by built-in fixtures or obstructed by vents or drains), commonly referred to as the “tiled area” of the room.

NOTE: Warmup Sticky Mats are safe (UL listed) for installation in showers, but it is recommended to use a separate mat or cable in the shower, so calculate the main area and the shower separately when heating a bathroom.

While the cables can be installed close to toe kicks, tubs, cabinets, and showers, they should be 2-4 inches away from the walls. To make sure you will have an adequate border, multiply the total tiled area by 0.9 to figure out the total heated area.

For bathrooms, subtract from the tiled area a section around the toilet flange large enough to keep the heating elements 6 inches away from the wax ring (usually 2-4 square feet).

Finally, select the length of cable (or cables) that covers the square footage closest to your heated area. Remember, you can connect up to three cables to one thermostat so long as the combined amperage is less than 15.

Shop Warmup Sticky Mats

Warmup Foil Heating Mats

Start by calculating the square footage of the open area(s) (anything not covered by built-in fixtures or obstructed by vents or drains), commonly referred to as the “tiled area” of the room.

NOTE: Warmup Foil Heating Mats are NOT safe (UL listed) for installation in showers.

While the mats can be installed close to toe kicks, tubs, cabinets, and showers, they should be 2-4 inches away from the walls. To make sure you will have an adequate border, multiply the total tiled area by 0.9 to figure out the total heated area.

For bathrooms, subtract from the tiled area a section around the toilet flange large enough to keep the heating elements 6 inches away from the wax ring (usually 2-4 square feet).

Finally, select the right size mat (or mats) to cover the square footage closest to your heated area. Remember, you can connect up to three mats to one thermostat so long as the combined amperage is less than 15.

Shop Warmup Foil Mats

WarmWire Cable

Start by calculating the square footage of the open area(s) (anything not covered by built-in fixtures or obstructed by vents or drains), commonly referred to as the “tiled area” of the room.

NOTE: WarmWire cables are safe (UL listed) for installation in showers, but it is recommended to use a separate mat or cable in the shower, so calculate the main area and the shower separately when heating a bathroom.

While the cables can be installed close to toe kicks, tubs, cabinets, and showers, they should be 2-4 inches away from the walls. To make sure you will have an adequate border, multiply the total tiled area by 0.9 to figure out the total heated area.

For bathrooms, subtract from the tiled area a section around the toilet flange large enough to keep the heating elements 6 inches away from the wax ring (usually 2-4 square feet).

Finally, select the length of cable (or cables) to cover the square footage closest to your heated area. Remember, you can connect up to three cables to one thermostat so long as the combined amperage is less than 15.

Shop WarmWire Cable Kits

Shop WarmWire Cable Spools

Get Started with Warm Your Floor

Knowing how to calculate your radiant flooring needs is crucial in achieving a system that is both efficient and effective. Remember, materials and design choices play a significant role in the overall functionality of your radiant floor heating. 

The Warm Your Floor team is full of experts who can help you figure out your heated area if you’re feeling stuck. You can share your plan details and get a formal quote on the materials that would be needed for your project by requesting a quote here. Simply include the drawing, your contact information, and your preferred product line if you have one.

8 thoughts on “Radiant Heat Layout Calculator: How to Determine Heated Area”

  • Sally Burch says:

    What should I use in the 2 inch space between the floor heating kit and the wall to make sure the floors are level?

    • Hi Sally,

      Assuming that this is for the standard heating mats and cable systems, you will need to thinset over the heating element. When doing so, you will make the thinset level over the rest of the subfloor. Feel free to give us a call if you have any further questions regarding this. Our number is 866-558-3369. Thanks, Sally!

      Warm Regards,
      Warm Your Floor Team

  • I would like to email the plans for the remodeled bathroom for an idea how much parts would be. Also, do folks typically run the warmer all the time? I am in Michigan the floor will be above a heated room. Using the warmer for tile comfort only the room has heat.

    Thanks, Bill

    • Jacquelyn Sutterman says:

      Hi Bill,

      You can email your plans to quote@warmyourfloor.com to get a formal quote on the materials that would be needed for your project. Simply include the drawing, your contact information, and your preferred product line if you have one.

      Most people use a programmable thermostat and set the system to run when they know people will be home and likely using the room. Occasionally customers will purchase non-programmable thermostats and leave them running continuously, but this leads to unnecessary energy costs. For this reason, the programmable option is always recommended.

      Warm Regards,

      The Warm Your Floor Team

  • I am planning on installing your WarmWire in a bathroom in the basement that has a slab. If it is about 30 sq ft that I need to cover, how much wire do I need to cover it and utilize the programmable thermostat?

    Thanks,
    Ken

    • Jacquelyn Sutterman says:

      Hi Ken,

      The old WarmWire cables were spaced at 2.5″ for standard heating or 2.0″ if you wanted a little extra heat when going over a slab subfloor. Current WarmWire cable is spaced at 3.0″ for standard heat and 2.5″ for extra heat.

      If you are interested in standard heat, you will need a 30 sq ft cable. We recommend using a SunStat Command programmable thermostat to control your floor. If you’d like to use the closer spacing for more heat you’ll need the 35 sq ft cable, which covers 29 sq ft at 2.5″ spacing.

      Warm Regards,

      The Warm Your Floor Team

  • If I measure and draw out my floor space. Can you figure out what I would need for my project? I am finishing off my basement and the tile areas I am thinking about heating.

    • Jacquelyn Sutterman says:

      Hi Kevin,

      Thanks so much for reaching out.

      Please do send us that drawing of your floor space & our quoting department will get back to you with a plan in 24 hours or less!

      Warm Regards,


      The Warm Your Floor Team

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