What’s the Right Size Hydronic Baseboard Heater?

Whether hydronic baseboard heaters make up your entire heating system or you use them as a supplement, finding the right size heater for each room can be a mystery.

Or maybe you’re replacing hydronic baseboard heater covers in a historic home and having trouble finding the right sizes.

We’re here to take the mystery out of hydronic baseboard heat. What size hydronic baseboard heater? Finding the right hydronic baseboard heater sizes is simple with a few calculations and the right resources.

Spacious bedroom with wood floors and white baseboard heaters.

How Much Heat Do You Need?

According to expert plumbers, when installing new hydronic baseboard heat, you’ll need to plan for about 34 BTUs per square foot. That number can change slightly depending on how well the space is insulated and ventilated.

Each linear foot of hydronic baseboard heating puts out about 600 BTUs when the water temperature is at 180 degrees F (see note).

Note: Please contact a plumber experienced with baseboard heat for further questions.


Tape measure across the top of a baseboard heater taking a measurement.

Calculating the Right Size Hydronic Baseboard Heater

Start by calculating the square footage of your space. Next multiply that by 34 BTUs to determine how many BTUs you need to adequately heat the room. Then divide that by 600 to find out how many linear feet hydronic baseboard heater you need in the room to produce that heat.

For example, a 10 x 10-foot bedroom is 100 square feet, (10 multiplied by 10 = 100) which requires 3,400 BTUs (100 multiplied by 34 = 3,400). You’d need 5.6 feet of baseboard heater to heat the space (3,400 divided by 600 = 5.6).

That’s it! You’ll want to install 5.6 feet of hydronic baseboard heater in the room (see note).

Note: Please contact a plumber experienced with baseboard heat for further questions.

Sizing for Baseboard Heater Covers

Once you've got the plumbing installed, it's time to turn your attention to the covers. These come in several shapes and sizes. Baseboarders slip on covers are built to fit standard hydronic heat systems. 

If you have older hydronic heating, look for a taller cover that accommodates their loftier profile. Baseboarders offers a tall cover just for this purpose. 

There are two categories of sizes, standard and custom:


Standard Size Baseboard Heater Covers

Most baseboard heater covers come in standard sizes, which can be cut to the right length. At Baseboarders, our standard sizes are 2, 3, 4-, 5-, 6-, and 7-foot lengths. For the best results, purchase a cover that is longer than what you require, then cut to the exact length you need. You can also request custom cuts directly from Baseboarders so all you have to do is install.

For instructions on how to cut Baseboarders in just a few easy steps you can do yourself, check this out.

How to Cut Baseboard Covers


If you need a baseboard heater cover that is longer than 7 feet, rather than purchasing a 7-foot piece and another shorter piece, we recommend splitting the difference. For example, if you have an 8-foot-long baseboard heater, order two 4-foot pieces.

The two pieces will need to be joined by a coupler and we think it looks best if that couple falls directly in the middle instead of at one end or the other.

Baseboard heater cover marked for trimming and tin snips poised to make a cut.

Non-Standard Cover Sizes

If you’re retrofitting your home for new covers, and you have non-standard sizes, it might seem like a challenge to find a good fit. Likewise, older hydronic baseboard heaters don’t always work well with today’s replacement covers.

However, Baseboarders is designed to fit over most baseboard heaters, no matter how old. It’s the perfect retrofit solution. 


Tall baseboard heater cover in white against a beige wall and dark wood floor.

Tall Covers

Our Premium Tall covers have the original styling of our Premium cover, but taller—2 inches to be precise. They come in 2-7' lengths and can be used for straight, inside, or outside corner applications.


Custom layout for a baseboard heater against a wood floor.

Custom Covers

Our Basic, Premium, and Elliptus, and Premium Tall offer different styles, but each can be customized in color and length. Custom cut sizes are free but has a little longer lead time and is non-refundable.

Ready to replace those baseboard heater covers? Even the difficult sizes are no problem at Baseboarders. Start shopping today.

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