How to Zero Iron Sights

Zeroing iron sights can be confusing, even for experienced shooters. You'll make "up" and "down" (elevation) adjustments using the front sight, but you'll make "left" and "right" (windage) adjustments using the rear sight. To make things even more confusing, the sights must move in opposite directions to zero. Let's get started.

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How to Zero Iron Sights

Whether you're zeroing a handgun or rifle's sights, the steps required to make adjustments are the same.

1. Get a target with 1" grid squares.

To accurately zero your irons, you'll need a paper target that's printed with a grid of 1" squares. This allows you to measure the distance between point of aim (POA) and point of impact (POI).

Virtually all iron sights are adjusted using MOA (minute of angle). MOA allows you to adjust your POA so that it matches POI at any distance. This is done by measuring that distance between POA and POI using your target, then adjusting your iron sights up or down, and left or right.

2. Know which direction to adjust your sights.

Many shooters adjust their iron sights in the wrong direction when trying to zero. there's an easy way to remember which direction you should turn each sight: An acronym, "FORS". This stands for "Front Opposite, Rear Same." 

What does that mean, exactly?

Always adjust the front sight in the opposite direction of your POI shift.

If your round impacts above the bullseye, you want to shift POI down. You will adjust the front sight up. 

If your round lands below the bullseye, you want to shift POI up. You will adjust the front sight down.

Always adjust the rear sight in the same direction you want to shift POI.

If your round impacts left of the bullseye, you want to shift POI right. You will adjust the rear sight right.

If your round impacts right of the bullseye, you need to shift POI left. You will adjust the rear sight left.

3. Know how to convert inches into MOA.

To zero, you'll use your grid target to measure the distance between POA and POI in inches. But you'll adjust your iron sights using MOA. The formula to remember is below:

[Distance between POA and POI in inches] divided by (Distance in yards / 100) = MOA

4. Know your sights' MOA per click.

Once you've converted your required adjustments into MOA, it's just a matter of turning your front sight up or down, and your rear sight left or right. But how many clicks do you turn each one? That depends on how many MOA each sight shifts with a single click.

Most iron sights use 0.25, 0.5 or 1 MOA clicks. Your iron sights will come with instructions describing MOA per click. Sometimes, the front and rear sights don't adjust by the same amount.  Daniel Defense's A1.5 sights (pictured above) provide 0.5-MOA clicks for the front sight, and 1-MOA clicks for the rear sight.

5. Know how sight radius affects MOA.

Sight radius is the distance between front and rear iron sights. This affects how much your point of impact will shift with a single click. This mostly affects rifle sights since barrel, handguard, and/or rail lengths can vary significantly. Most rifle sights' instructions specify the sight radius required to obtain a specific MOA per click.

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Zeroing Examples

Confused by all that math? Let's look at some visual examples and explain the adjustments needed to zero. 

25 Yards, 1-MOA irons

In this first example, we aim center of the target and see our round impacts low and left of the bullseye.

What adjustments must we make at 25 yards, with 1-MOA-per-click irons, to zero?

First, measure the distance from point of aim to point of impact:

Counting our 1" grids, we see our round landed 2.5" low and 2.5" left.

Second, use our inches-to-MOA formula to calculate adjustments:

[POA vs. POI in inches] divided by (Distance in yards / 100) = MOA

2.5 / (25 / 100) = ? MOA

2.5 / 0.25 = 10 MOA

We must adjust both sights by 10 MOA. 

With 1-MOA clicks, that's 10 clicks each.

Lastly, adjust our irons in the right direction. Remember, "FORS."

Since we landed low, we adjust the front sight 10 clicks down.

Since we landed left, we adjust the rear iron sight 10 clicks right.

50 Yards, Daniel Defense A1.5 irons

Remember that some iron sights adjust differently, like Daniel Defense's irons. Let's see how that would work. We fire aim the center of our target at 50 yards, but our round lands high and right.

Again, measure the distance from point of aim to point of impact:

We landed 4" high, and 2.5" right.

Now convert inches to MOA for windage and elevation:

[POA vs. POI in inches] divided by (Distance in yards / 100) = MOA

Elevation: 4 / (50 / 100), or 4 / 0.5 = 8 MOA

Windage: 2.5 / (50 / 100), or 2.5 / 0.5 = 5 MOA

Lastly, adjust our irons in the right direction:

Remember, the front sight adjusts 0.5 MOA per click, while the rear adjusts 1 MOA.

Elevation: 8 MOA / 0.5 per click = 16 clicks up.

Windage: 5 MOA / 1 per click = 5 clicks left.

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FAQ and Recap

We've covered how to properly zero iron sights, but you probably have some more questions. Here are common Q-and-A's, and the important stuff to remember from our guide.

Q: What if my rear sight adjusts both windage and elevation?

A: Some iron sights have a fixed front sight, so the rear sight provides all adjustments. If so, forget "FORS". Instead, always shift windage and elevation in the same direction as the intended POI (point of impact) shift. 

Q: What does "FORS" stand for, again?

A: "Front Opposite, Rear Same." This applies for conventional iron sights, where the front sight adjusts elevation, and the rear sight adjusts windage. Hit high? The front sight must be adjusted up. Hit right? The rear sight must be adjusted left, and vice versa.

Q: One more time, how do I convert inches into MOA?

A: [Distance between POA and POI in inches] divided by (Distance in yards / 100) = MOA

Q: What is the typical sight radius for AR-15 rifle irons?

A: For a rifle equipped with a carbine-length handguard, it's approximately 14.5". For a mid-length-equipped AR, it's approximately 17". This assumes the rear iron sight is installed as far back on the upper receiver as possible, directly above the handguard, while the front sight is instead at the far end of the handguard.

Q: Should I zero with the large or small peep sight? Does it matter?

A: Changing peep sights will not affect your zero. You should zero with the larger rear peep sight. This provides a clearer sight picture. The small peep sight is intended for long-distance shooting.