How to Measure for Gas Logs Step by Step

So you’ve looked over our guide to installing your new gas log fireplace, but there’s one thing you still need to determine, and that’s what size logs you should get. Gas logs come in all different configurations and sizes, and if you’re not very careful, you could end up with a set that’s too small for your firebox and doesn’t throw enough heat, or one that’s simply too large and either won’t fit or will cause a danger to your household.

So how do you know you’re getting a log set that’s perfectly sized for your fireplace, fire cabinet or firebox? The answer is simple: just measure it and do a few basic calculations. Check out this step by step set of instructions on how to measure for gas logs and how to make the calculations to be sure your new gas fireplace works perfect.

How to Measure for Gas Logs

The formula for how to measure for gas logs in a new fireplace is very simple, but clearance is absolutely essential. That is to say that your burner system has to have a specific amount of space between it and all four walls of the fireplace. The clearance you need depends on the specifics of your controls and system.

If you don’t meet the proper clearance, you can end up overheating and melting your gas valve. This won’t just cause your system to quit working, it can create dangerous conditions. For this reason, you definitely don’t want to just grab the biggest set you can—oversized logs are the top cause of system failure.

Measure first, before you buy your logs. The basic formula is front width x back width x depth. Be sure to get the right measurements in place and be accurate — measure at least twice for each dimension!

Measuring the Front Width

The front width of your firebox is the usable space between each side wall. It’s not the width of the opening, though the two could be the same if your fireplace opening fascia is even with your fireplace side walls. Otherwise, you’ll want to measure just inside the opening, from wall to wall, at the first point where you can get a full width measurement of the interior.

Measuring the Back Width

It’s very tempting to assume that the back width of your box will be the same dimensions as the front width. This can be a critical error, as some fireboxes are irregularly shaped and get narrower at the back end. Make sure you take a measurement at the narrowest point of the back of your fireplace.

Measuring Depth

The depth is the distance from the front of your fireplace to the back. Begin your measurement at the same point where you measured the front width and run it straight to the back wall. If your fireplace isn’t at least 14” deep, it’s probably not deep enough for any gas log set. You may want to consider a modified firebox or get an enclosed cabinet system instead.

Other Dimensions

Measuring these three dimensions and applying the earlier formula of front x back x depth will give you the overall dimensions of your fireplace. You may want to keep other dimensions in mind when you make a decision about your new log set. Height, for example, needs to be able to accommodate the size of the flame. For most fireplaces you want a height of at least 18 inches.

Center width is another important dimension to consider, as it’s where you’ll place the pilot and burner. This measurement is usually about seven inches back from the front width point. At this point, clearances are the most critical. If your fireplace seems to have an odd measurement or odd dimensions, the center width can be an excellent benchmark for the size of logs you need to buy.

Understanding Clearance

The measurements here will give you an idea of how much space you have in your system, but you still need to know what kind of clearance you need for the log system you choose. Each gas fireplace set will have an individual minimum clearance listed. A burner system with a safety pilot requires more than one without.

The reason pilots require more space is that a minimum amount of air flow is required to keep the control valve from melting or from overheating. This is the most common mistake people make when they buy log systems without performing size calculations. They simply buy the biggest, nicest looking logs they can squeeze in and ignore the clear warnings and recommendations that come with them.

Types of Ignition System

Ignition system for gas fireplaces basically come in three types, one without a pilot and two with pilots. The system you choose will determine the clearance you need and is as important for how to measure for gas logs as the dimensions themselves.

The first system is a simple manual on/off valve. Since there is no included pilot kit, all you’ll need is about two inches between the burner and sides. The second system is the manual safety pilot valve. For these, you’ll need at least double the space to protect the valve system. Finally, with a remote-ready pilot valve, you’ll need three times the amount of space as you would with a manual on/off switch.

Call in the Professionals

At Emberside, we make it a point to help you choose the best option for a gas log fire set for any home. We offer outstanding quality — among the best on the market today, with handcrafted composite logs that will look just like real wood, while offering the most efficient energy burning around. We are a family owned business with generations of expertise in what we do. We’ve been here for over 40 years, and we’ll be here for years to come.

Our logs are also designed for easy do-it-yourself installation, so you’ll never have to worry about additional costs in getting them set up. If you have any further questions about how to measure for gas logs or install your new system, start by checking out our products, accessories and other information and get in touch today!