How to Calculate the Right Scope Ring Height

June 15, 2022

How to Calculate the Right Scope Ring Height

Why is Scope Ring Height Important?

Generally, you want to mount the scope as close as you can to the bore without the scope touching the rifle. If the objective bell touches the barrel and the barrel whips while firing which they do, then it could affect your zero and even damage your scope. You use our parts finder tool, or you can use the formula below to determine the right height you need. 

How to Calculate Scope Ring Height for Your Rifle

Warne offers rings in various heights and diameters to accommodate most rifle scope combinations. To determine the required ring height, you must factor in scope tube radius, scope objective bell radius, and the thickness of your scope bases or rail.

Radius is ½ the diameter or diameter divided by 2.

In the example below we’ll use a 3-15x50 scope with a 30mm tube and we’re going to convert all our dimensions to inches since that’s how most ring heights (in the USA) are measured.

The formula is:

Or minus Tr minus Bh = Mrh

  • Or = Objective Radius
  • Tr = Tube Radius
  • Bh = Base or rail height measured at the front of the receiver
  • Mrh = Minimum ring height

The 50mm (glass) scope objective measures 58mm or 2.28 inches in diameter (divide by 2) and we get a 1.14-inch radius.

The 30mm scope tube is 1.18 inches in diameter, divide by 2 for a .59 inch radius.

We’ll be using a Picatinny rail in the example that is .312 inches thick at the front of the receiver.

1.14 - .59 - .312 = .238

Mrh = .238

We’ll need a set of rings that are at least .238 inches tall to fit the scope on this rifle, for Warne that will be a 30mm Low ring since our low rings measure between .250 and .275 depending on which style.

In a second example, we’ll use a 3-15 x 50 but with a 1-inch tube and a 2-piece base set.

The same 1.14 objective radius minus the .500 (radius of 1 inch tube) = .64 inches and our 2-piece front base is .150, so .64 minus .150 = .490 inch which would require a Warne 1-inch High ring to fit.

  • Or = 1.14
  • Tr = .50
  • Bh = .150

1.14 - .50 - .150 = .490

Mrh = .490

Other Factors When Determining Scope Ring Height

It’s also important to factor in rear sights or other modifications as these may require additional height to clear the scope over the firearm.

As a default, if you can’t find the exact objective radius, it’s safe to add 8mm to the manufactures’ “glass” dimension, so most 50 mm objectives are 58mm in diameter and so on…'

Once you calculated the scope ring height for your rifle check out our How To Choose The Best Rings For Your Rifle article.