How to Measure Scope Height and Why It Matters

When attaching a new scope to your rifle, one of the most important features that determine the accuracy, ease-of-use, and longevity of your scope will be its height. That’s why it’s so important to learn how to measure scope height and what the best fit for your chosen weapon and scope is.

Prior to starting, it’s important to note why the scope height matters. In fact, it is a crucial factor that will determine how accurate your weapon works and how comfortable you will be while using it. Mounting your scope correctly can also prolong its lifetime. If it is too high, this will put more force on it during a recoil, which may cause it to break over time.

Different scopes should be mounted at different heights, so there isn’t a one-size-fits-all solution, but the general rule is the lower the better, as long as your scope is not touching your rifle. The easiest way to find out what your scope height should be is to research your particular make of weapon and scope and ask at the point of purchase. In this guide, you will find out about some ways in which scope height is measured and why these can prove useful to you.

Step 1: Find Out the Ideal Scope Height 

In most cases, mounting your scope as low as possible is the way to go. This has three main benefits. Firstly, it will prevent your weapon from breaking under the torque and force it experiences during a recoil, thus saving you the money and time of purchasing a new one prematurely. Secondly, you will be more comfortable the lower your scope is mounted because the check resting height will be better.

Finally, accuracy can also be improved by lowering your scope height, which is especially important for precision shooting. The closer the scope is to your rifle, the more consistent your sight picture will be. This mainly affects long-range shots, so if you tend to shoot at a distance, mounting it lower is even more vital.

Objective Lens Size

The main factor that affects how low you can mount your scope is the size of your objective lens, which is the widest part of your scope. Many people opt for a 40-42mm lens, which usually allows you to mount the scope with low scope rings, but still offers good light transmission and optical clarity. If you use a larger 50mm lens, you’ll have to use high scope rings.

Step 2: Calculate the Height Using a Simple Formula

Once you know how low you can mount your scope, you’ll need a simple formula to calculate its height. The easiest one is as follows: objective lens diameter plus 2-4 millimeters to account for the scope body, then divide the resulting number by two. This will be your approximate scope height.

Sometimes, you may need a number that is more accurate. In this case, you can use a ruler to measure the diameter of the scope body at the objective lens, then divide it by two. Remember that if you need to convert inches to millimeters, you can simply multiply the measurement by 25.4.

Step 3: Find the Height to the Center Line of the Bore

Although these measurements can work well enough, they don’t account for certain additional factors such as the clearance needed for the bolt action, open sights, and more, which means that extra space can be necessary in certain cases. Sometimes, the sight height above bore, or the distance between the bore’s center and the objective’s center, needs to be taken into consideration. 

To calculate this, several procedures are possible, but the simplest one that can get you a decent measurement is to measure the distance between the barrel’s center and the scope or scope rings’ center. In many cases, this can be all you need.

A More Accurate Measure

If you need a slightly more accurate measure, you can use this simple formula involving three measurements. First, measure the bolt and then divide this by two. Then do the same with the scope tube. Finally, measure the distance between the top of the rifle bolt and the bottom of the rifle scope and add up all three numbers.

Step 4: Consider the Scope Rings 

A final factor that’s often forgotten is the height of your scope rings. If they are too high, your accuracy will be compromised, and when you mount them too low, you run the risk of your scope hitting the barrel of your rifle, which you must avoid. That’s why it’s important to measure your scope rings and find that sweet spot in the middle.

Start by measuring the distance between the ring’s center and its receiver contact point. Generally, using a ruler should be accurate enough. Next, find the distance between the center of the bore and the center of the objective lens. You can then measure how far apart the receiver and scope are and add this to the other two numbers. Aim for the lowest height possible that still allows your scope to stay clear of the barrel.

Choosing Scope Rings

When choosing your new scope rings, make sure they are the best fit possible. There are a few things to consider aside from their height, so check your chosen rings are the best fit possible. The most common scope tubes have diameters of 1 inch, 30 mm, or 34mm, so getting rings that fit your model is your most important consideration.

However, don’t forget to also check how your new scope rings will be attached. Traditional ones will need a hex tool, but more modern ones may be simply screwed on.


Scope height is of crucial importance to ensure your scope will be as accurate, comfortable to use, and durable as possible. When figuring out how to measure scope height, some simple formulas are generally enough, allowing you to mount your scope as low as possible while still preventing it from touching the barrel. By performing these simple calculations, you can ensure that your shooting experience will be precise and pleasant.

Joseph Fox

Joseph Fox

Joseph Fox writes on a variety of topics ranging from reloading ammunition to gun cleaning. He has been featured on various publications like thetruthaboutguns, Sofrep & many more. Joseph is also the founder of Gunloading, where he reviews different types of reloading & firearm products available on the market.