How to Measure for a Fireplace Insert

Replacing a fireplace with a fireplace insert is a great way to update your space and heat your rooms more effectively with less effort and maintenance. These functional decor pieces can work in a variety of spaces, as long as they fit correctly into your existing fireplace. In order to make sure you purchase the best fireplace insert for your space, it is imperative that you accurately measure the area to obtain the correct dimensions. Read on to find out how to measure for a fireplace insert.

Getting Your Fireplace Dimensions

Since there are a range of fireplace insert sizes, the key factor in selecting the correct one is based on the size of your fireplace. When you measure your fireplace, make sure you are sizing the opening, which is also known as the "firebox" or "cavity," at different points so you can get accurate fireplace dimensions for your fireplace insert. To learn more about fireplace inserts, read our guide: What Is a Fireplace Insert?

To get your fireplace dimensions you will need to calculate the length, height, and depth to measure for your fireplace insert. If your fireplace has an arched opening, take measurements of the highest and lowest point and select the smallest number.

Length:Take the length from the left side of the fireplace to the right. Be sure to measure at both the opening and the back of the fireplace because they numbers can differ. Generally speaking, you will want the smallest of these measurements to ensure the insert will fit.

Height: Measure the height from the floor of the firebox to the top. Measure in both the front and back to ensure an optimal fit. If your fireplace has a protruding lintel (the iron rod that runs from front to back of the ceiling of your fireplace), then add 1/8 inch space to create enough clearance room.

Depth:For the depth, measure the distance from the fireplace opening to the back wall of the firebox. Be sure to record these fireplace dimensions from the center of the firebox.

Tip!

Keep in mind the clearance requirements for the insert. This refers to the space that is required above, behind, and around the fireplace insert to protect its surroundings from the heat. Some electric inserts require no clearance since the heat is self-contained and well insulated, but a general rule of thumb is to allow all inserts 1-2 inches of clearance space.

Mantel

The mantel is the outer frame of the fireplace that is usually decorated. It should be at least 12 inches above the fireplace opening. When measuring the mantel or space for a mantel, bear in mind that the top and bottom lengths can differ.

Length:Mantels can differ from house to house – some reach from one end of the wall to the other, while others are only a little larger than the firebox itself. For this reason you best bet is to select a mantel 12 inches longer than the firebox. For example, if your firebox measures 42 inches in length, then you would want to choose a mantel that is 56 inches long.

Height: A fireplace in a smaller space would do well with a mantel that has a 4 – 5 inch face height. A 6 inch mantel face height would do better in a larger room.

Depth:Mantels are typically 10 – 12 inches deep, however you need to take into account the amount of traffic that occurs around the fireplace. Consider any surrounding furniture, the size of the room, and the aesthetic you prefer.

Tip!

User a laser distance tape measuring tool for more accurate measurements.

What Heating Needs Does Your Room Require?

Measuring for a fireplace insert will include the size (in square feet) of the room so that you know how many BTUs (British Thermal Units) your space will need. The larger the size of the room, the more heat you will need, which will in turn determine which type of fireplace insert you should choose. The shape of your room will affect the way you calculate the area.

Rectangular Room: Measure the length and width of your room and multiply those numbers.

Triangular Room: Measure the length and width of the room. Multiply those numbers and then divide by 2.

Circular Room:Measure the distance from one wall to the center of the room. Take this number and multiply it by itself and then by 3.1416 which is a rounded form of π (pi).

Once you have the area of the room, multiply that number by 20 to get the minimum number of BTUs you will need to efficiently heat your room. For example, a room that is 500 sq. ft. would need a fireplace insert with at least 10,000 BTUs.

Tip!

If your room has multiple shapes, it is a good idea to divide it into rectangles, triangles, and circles to more easily do these calculations. Then you can add those values together.

Now you know how to measure for a fireplace insert, you will be able to accurately obtain your fireplace dimensions and choose the best insert for your home.