Electric Fireplace Insert Sizes: How to Measure

On this page (9 sections)

1. How do you measure an electric fireplace opening?
2. How much clearance should you leave around an insert?
3. How do you measure depth and make room for the cord?
4. What if your firebox is uneven or tapered?
5. Can you use an electric insert in an old fireplace?
6. Which insert suits your opening and installation?
7. What mistakes cause insert fit problems?
8. What should you check before choosing a size?
9. Which electric fireplace insert size should you choose?

An electric fireplace insert size guide helps you match a unit to an opening before you buy. Measure the smallest clear width and height, check usable depth, and compare all three with the insert’s full outside dimensions.

A “23 inch” or “33 inch” label is a size class, not a promise that the unit will fit an opening of that exact width. The outside dimensions may be wider, taller, or deeper than the number in the name.

How do you measure an electric fireplace opening?

Measure the clear width, height, and depth of the space where the insert will sit. Record each in inches, and use the smallest reading if the opening varies.

1. Measure the width near the top, middle, and bottom.
2. Measure the height along the left, center, and right.
3. Measure depth from the front edge to the first obstruction at the back.
4. Note raised hearths, trim, lips, and uneven surfaces that could affect placement.

Keep the tape level and check the opening from both the front and farther inside. If the front is wider than the back, record both measurements because a tapered firebox can stop an insert from sliding in.

A cardboard template cut to the unit’s outside width and height can help you check whether it can pass through the opening. It won’t account for a plug, cord route, or required clearance, so check those separately.

Which measurements matter in an electric fireplace insert size guide?

The smallest opening width and height, plus usable depth, are the starting points. Then compare them with the unit’s full dimensions and account for the plug, cord, support, and installation instructions.

Names such as “28.5 inch” often describe a nominal width. The PuraFlame Klaus is called a 33 inch insert, but its overall dimensions are 35.04 in wide, 26.96 in high, and 8.78 in deep.

The Giantex is 28.5 in wide, 21 in high, and 6 in deep. Its smaller width and depth may suit a narrower space, provided the opening and installation method match its instructions.

For a recessed installation, also check how much depth an electric fireplace needs. A unit can fit across the opening and still project too far or leave too little room for its plug.

How much clearance should you leave around an insert?

Leave the clearance required by that unit’s installation instructions. There isn’t one universal gap for every insert and firebox.

A close fit can make installation difficult, while a larger gap may need a trim kit or surround. Check whether the unit sits on the floor, slides into furniture from behind, or attaches to a wall, since the method affects how it enters and finishes at the opening.

Don’t trim a firebox or force an insert into a tight opening to make the measurements work. If you expect a gap around the unit, compare the options in our guide to electric fireplace insert trim kits.

How do you measure depth and make room for the cord?

Measure from the front edge to the nearest obstruction, then confirm that the body, plug, and cord route all fit. A cavity can be deep enough for the unit but too shallow for the plug behind it.

The Innoflame 23 Inch Log Insert measures 24 in wide, 20.2 in high, and 5 in deep. Its furniture opening guidance is 23 in wide by 19 3/4 in high at the front, with a minimum rear opening of 24 in by 20 3/16 in.

This insert slides forward into the furniture cavity from behind. Choose it when you can reach the back of the mantel or TV stand, and skip it if the furniture cannot be accessed from the rear.

The VEVOR 35 Inch Insert measures 35.04 in wide, 26.97 in high, and 5.91 in deep. It is designed for recessed or wall mounted installation, so follow its instructions for the setup you choose.

For another fit check, compare 23 inch electric fireplace inserts for cabinets. Cabinet openings and old masonry fireboxes have different constraints, so follow the instructions for your specific unit.

What if your firebox is uneven or tapered?

Use the smallest clear width and height when checking fit. Old masonry, trim, and firebox walls may not form a perfect rectangle.

If the opening narrows toward the back, measure its width and height there too. Look for projecting bricks, a raised floor, or a sloped surface that could prevent the insert from sitting flat.

A template helps test whether the face can pass through the opening, but it won’t confirm the depth or cord space. Check those with a tape measure and the unit’s instructions.

Can you use an electric insert in an old fireplace?

Sometimes, if the opening, installation method, and electrical setup meet the unit’s instructions. Dimensions alone don’t confirm that an old fireplace is ready for an insert.

Check whether the existing fireplace needs changes and whether there is a suitable outlet. Don’t assume a working wood or gas firebox is ready for an electric unit just because the opening seems close.

The PuraFlame Klaus can sit directly on the floor and plugs into a 120 V outlet, but it cannot be hardwired. Its instructions also say the chimney should be blocked when replacing an old fire, so account for that requirement before choosing it.

If you’re weighing another fuel type, compare electric fireplace inserts with gas inserts. For a traditional log appearance, these electric fireplace inserts with logs offer more options to consider.

Which insert suits your opening and installation?

Choose by the measured opening and installation path first, then weigh appearance and heat settings. A product’s width label is only a starting point.

The Innoflame suits a furniture cavity with rear access because it slides in from behind and gives front and rear opening measurements. Skip it if the furniture is fixed against a wall with no access behind it.

The Giantex is a compact option for an opening that can take its 28.5 in width and 6 in depth. It can be recessed into a cabinet or wall, or used freestanding, so it fits projects where you want more than one installation approach.

The PuraFlame suits a traditional fireplace look with its resin log, grate, brick-style interior, glass door, and mesh screen. Choose it when the larger 35.04 in overall width and 8.78 in depth fit, and an outlet is available.

The VEVOR suits a wider opening and buyers who want several flame color and brightness settings. Its 35.04 in width still needs to fit the measured space, and its recessed or wall mounted setup should follow the installation instructions.

What mistakes cause insert fit problems?

The most common mistake is choosing by the size in the product name. A 33 inch insert can be more than 35 in wide, so compare the full outside dimensions with your opening.

Another mistake is measuring only the front face. A tapered cavity, projecting brick, or obstruction at the back can prevent the unit from sliding fully into place.

Don’t overlook the cord and plug, or plan to compress the cord behind the unit. Confirm where the cord exits and keep the outlet accessible as required by the instructions.

Finally, don’t assume that a trim piece solves every gap or clearance problem. Confirm the support, finishing method, and required clearances before installation; see how an electric fireplace fits a wall, recess, or insert opening if you’re still deciding on the setup.

What should you check before choosing a size?

Compare the smallest opening measurements with the insert’s full dimensions, then confirm depth, cord space, support, and installation clearances. A nominal size alone cannot confirm fit.

Keep a note of the opening’s width, height, and depth, including any rear measurements or obstructions. Check the unit instructions for model-specific opening dimensions and setup steps before you buy.

Choose a smaller unit only if its installation instructions allow the fit and you have a plan for the visible gap. Choose a wider model only when the opening, installation path, and finish plan all accommodate it.

Which electric fireplace insert size should you choose?

The right insert is the one whose full dimensions and installation requirements match your measured opening. This electric fireplace insert size guide comes down to three checks: smallest width and height, usable depth, and a safe path for the plug and cord.

Choose the Innoflame when you have rear access to a furniture opening and its stated front and rear measurements fit. Consider the Giantex for a more compact installation, the PuraFlame for a traditional log and brick look, or the VEVOR when a wider unit and multiple flame settings suit the space.

If the opening needs a finished edge, review the trim kit guide before deciding. For help choosing the installation style, read our guide to electric fireplaces for walls, recesses, and inserts.

Frequently asked questions

How do I measure a firebox for an electric insert?

Measure the opening’s width, height, and depth in inches. Check width and height at the front and farther inside, since a firebox may taper or have uneven edges.

Use the smallest clear measurements, then compare them with the insert’s full outside dimensions and required clearances.

Should an electric fireplace insert be smaller than the opening?

It depends on the unit and how you plan to finish the gap. Some inserts sit inside a firebox with a trim kit or surround, while others are designed to fit a furniture opening closely.

Check the installation instructions for fit, support, and clearance requirements before choosing.

Does insert depth include space for the power cord?

The body depth describes the unit itself, but the cord and plug also need room. Check where the cord exits and how the instructions route it.

Don't pinch the cord behind the insert or block the outlet to make a unit fit.

Can I install an electric insert in any old fireplace?

No. The opening needs to fit the insert, and installation must follow the unit’s instructions.

Check for a suitable outlet, room for the cord, and requirements for the existing fireplace or chimney.

Don't assume a unit can go into a working wood or gas firebox unchanged.