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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Heated Floor Area FAQs
What’s the difference between total floor area and heated floor area?
Total floor area includes the full room blueprint, heated floor area is only the portion you need heated. This excludes built-ins like vanities, cabinets, and appliances. Only walkable surfaces should be part of your heat coverage.
How close can heating cables or mats be installed to walls or fixtures?
Keep all heating elements 2–4 inches from walls and baseboards. Around toilets, leave at least 6 inches between the heating element and the wax ring. This prevents uneven heat and protects components from excessive temperature exposure.
How many thermostats do I need for my heated floor?
Most radiant heating thermostats can handle up to 15 amps on a single circuit. That typically covers one medium-to-large room, or up to three mats or cables if their combined load doesn’t exceed the thermostat’s rating. For larger or separate areas, use an additional thermostat for heat control.
Can I heat multiple rooms with one system?
Yes, but each area must share the same circuit and thermostat. It’s best to separate rooms that have different flooring materials, insulation, or heating needs. That way, each thermostat can control temperature independently from each other.
What if my calculated heated area falls between mat or cable sizes?
Always round down to the nearest available size. It’s safer to have slightly less coverage than risk overlapping or excess cable, which can cause overheating. Heat naturally spreads across tile, so small gaps won’t create noticeable cold spots.