How do you measure a fireplace opening?

Author: Earl Christiansen  |  Last update: Monday, April 21, 2025

To measure for an outside fit, take the height on the left side, the middle and the right side of the fireplace opening. Then, measure the width in three places; top, middle and bottom. To check and see if your fireplace opening is square, measure from the bottom left corner to the top right corner.

What is considered the fireplace opening?

The fireplace opening, also known as the firebox opening, frames the fire and plays a pivotal role in the overall design of the fireplace. Its dimensions, shape, and surrounding materials influence the visual impact of the hearth, making it a key consideration in achieving the desired aesthetic for your living space.

How to calculate fireplace size?

How to size your fireplace
  1. Calculate your room's volume (m3). Measure your room width, length and height. Multiply those figures with each other to get your room volume.
  2. Multiply the cubic metres (volume) by the relevant insulation factor below: Poorly insulated room: 0.06. Well-insulated room: 0.035.

How wide is a 42 inch fireplace?

SPECIFICATIONS:Fireplace Dimensions-42" W x 19.3" H x 5.55" D. Insert Dimensions: 41" W x 18.23" H x 5.71" D.

How do you measure the width of a fireplace?

To measure for an outside fit, take the height on the left side, the middle and the right side of the fireplace opening. Then, measure the width in three places; top, middle and bottom. To check and see if your fireplace opening is square, measure from the bottom left corner to the top right corner.

How to Measure for your Fireplace Insert

What is the diameter of a standard fireplace?

Standard Fireplace Dimensions

The typical dimension in inches of a standard fireplace when it comes to width, height, and depth are 28-48 x 20-30 x 16-24. These dimension measurements will change depending on the type, placements, and other factors.

How wide is a typical fireplace mantel?

Our most popular styles are 68” wide, but ours will range from 55”-84” wide with some custom designs even larger. The wall and the firebox width as well as the ceiling height provide insights on choosing a size that is appropriate for your fireplace.

What is the size of a fireplace in a house?

Standard fireplace dimensions depend on whether it's a gas or wood-burning fireplace. While there is no set fireplace size, our Timeless Series, which has a standard fireplace size, ranges from 36” to 48” wide and 21” to 48” tall.

How to measure fire opening?

How to Measure a Fireplace Opening
  1. Height – Up and Down. Using measuring tape, record the height of your firebox from the opening, the rear and the lintel (more on this in the next paragraph). ...
  2. Width – Left to Right. ...
  3. Depth – Front to Back.

Are fireplaces measured diagonally?

Another thing to consider is whether you will place a TV above the wall fire. If you will, the fire's size must balance the TV's. That means the fireplace must be at least as wide as your TV. Remember the fireplace size is measured by the actual width, and TV size is measured diagonally, when noting the dimensions.

How do I find the make and model of my fireplace?

The model and serial numbers are located on a “rating plate,” which is a metal plate that's usually permanently affixed to the fireplace, insert or stove. In gas fireplaces, the rating plate is found in the controls area.

How to calculate fireplace opening?

the 1⁄65 ratio to large rooms (Ref. 1). A fireplace opening's height-to- width ratio should be between 1:1 and 1:2. Not only is a wider open- ing more pleasing aesthetically, but a tall, narrow opening is more like- ly to release smoke into the ro o m .

What is the 10 2 fireplace rule?

This rule means that the chimney's shortest side needs to be at least 3 feet above roof penetration, and its top has to be 2 feet higher than any part of the building within 10 feet.

Can a fireplace opening be too big?

For example if the inside dimensions of the flue are 10 x 10 equalling 100 square inches, then the fireplace opening should not exceed 10 times this or 1000 square inches. If a fireplace opening is too large it will allow more air into the fireplace than the flue can exhaust.

How to measure fireplace size?

Getting Your Fireplace Dimensions
  1. Length: Take the length from the left side of the fireplace to the right. ...
  2. Height: Measure the height from the floor of the firebox to the top. ...
  3. Depth: For the depth, measure the distance from the fireplace opening to the back wall of the firebox.

What is code for distance between fireplace and mantel?

National Standard Building Code Information

2114.3 Masonry-built Fireplaces 4114.3. 10 - All combustible mantels and similar trim shall be kept at least 6 inches from the fireplace opening.

How far should a fireplace opening be from the mantle?

National building codes specify minimum distances between the top of the fireplace opening and the bottom of the mantel to prevent fire hazards. While codes can vary, a common specification is that mantels must have at least a 6-inch clearance from the fireplace opening for every 1/2 inch that the mantel protrudes.

What is the average opening for a fireplace?

Standard fireplace opening dimensions

Average opening sizes range from 36-48 in (91-122 cm) in width and 20-30 in (51-76 cm) in height.

How high should a fireplace opening be?

We have also seen some historic kitchens with the original fireplace opening placed 36 to 42 inches off the floor, and in that context, it looks great. There really are no 'rules', as long as you remember that the best view of the flames is looking down into them.

How to determine fireplace mantel size?

Width: The mantle should be wider than the fireplace — typically 3 to 6 inches wider than the firebox on each side. You can choose to go wider, but it's best to keep the mantel width proportionate to the room size and the fireplace. Height: The standard mantel height is about 4-1/2 feet above the hearth's floor.

How much space should be on either side of a fireplace?

2. Leave Room For Your Fireplace Surround. Regardless of how small you go with your fireplace opening width, don't forget about the surround. When you envision the design of your fireplace, be sure to add 12 to 24 inches on either side of the fireplace for a surround.

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