How to Calculate What Scope Ring Height I Need

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What Size Scope Rings Do I Need for My New Chassis System?

What size of scope rings do I need? This is a common question that must be answered first to avoid buying the wrong scope rings. It is very difficult to give an accurate scope ring height measurement without all of your components in hand. For this reason, we have provided a scope ring height formula to help you determine the required proper scope ring height. The formula will vary slightly depending on the type of chassis you are measuring for.

The Formula for Scope Ring Height

How ring heights are measured? Here's a formula in finding the right scope ring height. It will work with most rifles designed from the factory to have a scope mounted on it.

(All units in inches. Ring height measured from top of base to scope center line. Sloped bases add .035" to height every six inches objective extends from base.)

For standard Evolution chassis: (actual objective diameter/2) + .9 - (action diameter/2) - base height = required ring height.

For Evolution HD / Carbon chassis: (actual objective diameter/2) + 1.05 - (action diameter/2) - base height = required ring height.

We will now work through an example using the formula for a standard Evolution Chassis:

Using the above formula, we will plug in some numbers. Our rifle scope in this example has an objective lens diameter of 50 mm. We must convert this to inches, which comes to 1.96. The Remington 700 SA has an action diameter of 1.35 inches. Finally, our scope base is un-sloped and has a height of .350 inch from the bottom of the base to the plane in-between the risers on the Picatinny rail.

The equation is solved in the above photo. In our example we need .855 inch of ring height. Our scope has a 30mm tube, so we choose the XLR 30mm Medium Profile Scope Rings which have a height of 1.18 inches. The extra space should be enough for our lens covers.

The use of a caliper is recommended for taking measurements. It is also important to note that all units are in inches-be certain to convert before placing your dimensions into the formula. The formulas provided do not guarantee the correct fit. Use your own discretion.

If you need help finding the correct ring height, contact us today. Email us at info@xlrindustries.com.