Eye Relief for Tactical Scopes: How to Choose Yours

How Do I Measure My Own Eye Relief?

To find your ideal eye relief measurement, you must determine the distance from your eye to the optic when your cheek is firmly pressed against the stock. You can do this using a standard tape measure or a ruler.

Setting Up the Measurement

Mount a scope or a similar optic onto a mock-up or a real rifle. Position the rifle in a way that mimics your natural shooting posture, ensuring the stock is at the height where your cheek would naturally rest during a shot.

Taking the Reading

Lean your face against the stock and look through the optic. Move your head forward and backward until you see the clearest, most complete image without any black shadows or “tunneling” at the edges of the glass. Measure the distance from your eye to the front lens in mm. This number represents the eye relief you need to seek in a tactical scope.

Finding the Value on a Product

Manufacturers usually list the eye relief in mm in the technical specifications section of the product documentation. If it is not listed, it is often because the optic is designed for a standard range, but you should check the manufacturer’s website to confirm the specific mm value before ordering.

What Happens if the Eye Relief is Wrong?

Choosing an eye relief value that does not match your physical requirements results in two specific issues: scope shadow or a restricted field of view.

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The Result of Too Short a Value

If the eye relief measurement is too short for your face, you will experience “scope shadow.” This occurs when your brow or cheek physically blocks the light entering the lens, creating a dark blur around the edges of your vision. Because you cannot physically move your head further forward, the only way to see the full image is to move the entire rifle further away from your body, which ruins your cheek weld and stability.

The Result of Too Long a Value

If the eye relief measurement is too long for your face, you will experience a restricted field of view. You may be forced to pull your head back so far that you cannot maintain a consistent cheek weld on the stock. This creates a gap between your face and the rifle, making it difficult to stay steady and causing the optic to feel like it is “floating” away from you.

What if I Fall Between Two Eye Relief Values?

If your measurement falls exactly between two standard options, such as 3.0mm and 3.5mm, you should choose the larger measurement.

Why You Should Choose the Longer Value

A longer eye relief is generally easier to accommodate than a shorter one. If an optic requires 3.5mm of space and you only need 3.0mm, you can simply sit slightly further back. However, if an optic only allows for 3.0mm and you need 3.5mm, there is no way to move the optic “further away” from your face without changing the mounting hardware or the rifle’s stock.

Checking Return Policies

Because eye relief is a physical fit that cannot be adjusted after the optic is mounted, check the seller’s return policy regarding sizing and fit. Many retailers allow for returns if the optic does not provide a clear view, but confirming this before you buy can prevent a difficult return process.

Reviewed by the RecommendedOptics editorial team. RecommendedOptics writes these guides from the 28 most-reviewed tactical scopes listings in our retail dataset, not from manufacturer copy.