AR-15 Zero Calculator and 5.56 Bullet Drop Chart

By Matt Rice, Owner of Ozark Armament. Matt has zeroed hundreds of rifles across dozens of calibers in 10+ years of working with optics, iron sights, and mounting systems.

Zeroing your rifle optic is one of the first things you do after mounting it, and one of the most commonly overthought. “Should I zero at 25 yards or 50? What about 36? What’s a 50/200 zero?” The answer depends on your caliber, your optic height, and what you plan to use the rifle for.

This calculator cuts through the noise. Answer four questions about your setup, and it will recommend the optimal zero distance with a complete holdover table so you know exactly where your bullet lands at every range.

5.56 Bullet Drop Chart

Want the numbers without running the calculator? These charts show where a 5.56 NATO round lands relative to your point of aim at common ranges, for the two most popular zeros. Values are in inches: a positive number means the bullet is above your point of aim, a negative number means it is below. Both charts assume a standard red dot at 2.6 inches over bore and standard atmospheric conditions. For your exact ammo, optic height, and use case, use the calculator above.

5.56 Bullet Drop Chart: 50-Yard Zero (50/200)

5.56 Bullet Drop Chart: 100-Yard Zero

The 50-yard zero keeps you within about 2 inches of your aim point all the way to 200 yards, which is why it is the most common choice for a 5.56 carbine. The 100-yard zero gives you a dead-on hold at 100 and a cleaner reference for longer shots where you dial or hold over. Heavier 62gr loads drop a little faster past 200 yards than 55gr, as the charts show.

How to Use This Calculator

Select your ammunition from the dropdown. We’ve included the most common factory loads for 5.56 NATO, .300 Blackout (supersonic and subsonic), 7.62x39, 6.5 Creedmoor, and .308 Winchester. If your exact load isn’t listed, pick the closest match in the same caliber and bullet weight range.

Next, select your optic type. This determines your height over bore (HOB), which is the vertical distance between the center of your barrel and the center of your optic. A standard AR-15 red dot at lower-third co-witness is about 2.6 inches. A taller mount like a Unity FAST is 3.3 inches. If you're running irons instead of a red dot, check out our iron sight options. The calculator uses this to compute how much your bullet drops relative to where your optic is pointed.

Finally, choose your primary use case. Home defense, general purpose, hunting, precision, and military BZO all have different optimal zero distances. The calculator explains why each recommendation works for that use case.

How the Math Works

A bullet exits the barrel below the line of sight. Your optic sits above the bore by 2-3 inches (height over bore). To compensate for gravity, the barrel is angled slightly upward relative to the sight line. This means the bullet’s parabolic arc crosses the line of sight twice: once on the way up (your near zero) and once on the way down (your far zero).

Between those two points, the bullet is above your point of aim. Beyond the far zero, it’s below and dropping fast. A 50/200 zero, for example, means the bullet crosses the sight line at roughly 50 yards and 200 yards. At 100 yards, it’s about 1.7 inches high.

For hunting, the calculator uses Maximum Point Blank Range (MPBR) optimization. It finds the zero distance that keeps the centerline trajectory within your effective vital zone for the longest practical range. This is the zero that lets you aim dead-center on game without holdover once close-range height-over-bore offset is accounted for.

MPBR is a centerline trajectory calculation. It assumes the center of your group, or point of impact, follows that path. It does not include rifle/ammo group size, shooter wobble, wind, or a safety margin. For field use, enter an effective vital zone after subtracting those margins. For example, if your rifle and ammo produce a 1.75-inch aggregate group and the actual vital zone is 6 inches, use about a 5-inch effective zone for a basic margin or 4.25 inches for a more conservative margin.

The trajectory data comes from pre-computed ballistic tables using published drop values from Federal, Fenix Ammunition, Eagle Eye, and Army ballistic research. We validated results against 32 known-good data points from multiple authoritative sources.

Common Zero Distances Explained

25-Yard Zero

The U.S. Army uses a 25-meter zero (essentially 25 yards) because most indoor ranges max out at 25 yards, and the math works out so the bullet crosses the sight line again at roughly 300 yards. Soldiers zero at 25 meters using a scaled silhouette target with a 1.5 MOA ballistic offset. It’s practical for military use, but at intermediate ranges (100-200 yards), the bullet can be 6-9 inches above point of aim, which means less precision for civilian shooting.

36-Yard Zero

The USMC battlesight zero (BZO). A 36-yard zero flattens the trajectory so the bullet stays within about 4 inches of point of aim from 0 to 300 yards. It’s a good compromise between the Army’s 25-meter zero and a flat 50-yard zero, and it works well with BDC reticles calibrated for 300-yard engagement.

50-Yard Zero (50/200)

The most popular civilian zero for 5.56 AR-15s. The bullet crosses the sight line at 50 yards, rises to about 1.7 inches high at 100 yards, and crosses back down at roughly 200 yards. This gives you less than 2 inches of deviation from 0 to 200 yards, which is close enough to aim center-mass and hit at any practical carbine distance.

100-Yard Zero

Standard for precision rifles, bolt guns, and any setup where you’ll be dialing turrets or using holdover marks for distance. The bullet is dead-on at 100 yards. Beyond that, you hold or dial. This is the default for .308 Winchester and 6.5 Creedmoor when paired with quality AR-15 scopes. It gives you a clean, simple reference point.

MPBR Zero (Hunting)

Maximum Point Blank Range optimization finds the zero distance that keeps the centerline trajectory within your target’s vital zone for the longest possible range. With the default 5.56 NATO 55gr preset, standard red dot height, and a 6-inch vital zone, the calculator returns about a 215-yard zero and a 250-yard MPBR. Use a smaller effective vital zone when you need room for group size, wobble, wind, or safety margin. This is ideal for hunting where range estimation is imprecise and shot opportunities are time-limited.

Why Height Over Bore Matters

Your optic sits above your barrel. The bigger that gap, the more pronounced the offset at close range. With a standard 2.6-inch height over bore, your bullet hits about 2.6 inches below your point of aim at the muzzle. At 5-10 yards, it’s still 2+ inches low. Running backup iron sights for AR-15 gives you a lower height over bore option. This is why close-range offset training matters for home defense and CQB.

Taller mounts like the 1.93-inch and Unity FAST (2.26-inch) are popular for heads-up shooting posture and night vision compatibility. But they increase close-range offset. A Unity FAST mount puts the optic 3.3 inches above the bore, meaning your bullet hits 3.3 inches below point of aim at contact distance. The calculator accounts for this automatically based on your optic selection.

A Note on Subsonic .300 Blackout

Subsonic .300 Blackout (220-grain loads at ~1,010 fps) has a radically different trajectory than any supersonic rifle cartridge. It drops 9+ inches between 50 and 100 yards, and over 54 inches by 200 yards. A 50-yard zero is the most practical choice because it keeps the math manageable at short range. Beyond 75 yards, significant holdover is required. The calculator reflects this steep drop curve accurately.

Frequently Asked Questions

What is the best zero distance for an AR-15?

For most AR-15 shooters using 5.56 NATO, a 50-yard zero is the most versatile choice. It keeps bullet impact within 2 inches of your point of aim from 0 to 200 yards. If you primarily hunt, an MPBR zero can extend your point-and-shoot range when the effective vital zone includes room for group size and field conditions.

How much does a 5.56 round drop at 300 yards?

With a 50-yard zero and a standard red dot, a 55gr (M193) 5.56 round hits about 13 inches below your point of aim at 300 yards, and a 62gr (M855) round about 15.5 inches low. With a 100-yard zero, expect roughly 17 to 19 inches of drop at 300 yards. See the bullet drop charts above for the full range breakdown.

What is a 50/200 zero?

A 50/200 zero means your bullet crosses the line of sight at approximately 50 yards (near zero) and 200 yards (far zero). Between those distances, the bullet is slightly above your point of aim (about 1.7 inches high at 100 yards). This is the standard civilian carbine zero for 5.56 NATO.

What is height over bore and why does it matter?

Height over bore (HOB) is the vertical distance from the center of your barrel to the center of your optic. On a standard AR-15 with a red dot at lower-third co-witness, this is about 2.6 inches. It matters because at very close range (0-25 yards), your bullet impacts that many inches below where your optic is pointed. Higher mounts mean greater close-range offset.

What is Maximum Point Blank Range (MPBR)?

MPBR is the maximum distance at which you can aim dead-center on a target and keep the center of your group inside a chosen vital-zone envelope without holdover. The calculator finds the zero distance that keeps the centerline trajectory within your specified effective vital zone out to the farthest possible distance. For the default 5.56 55gr preset with a standard red dot and a 6-inch zone, the MPBR is about 250 yards with a 215-yard zero. For field use, reduce the entered zone for group radius, wobble, wind, and safety margin.

Why does the Army zero at 25 meters?

Most military ranges have a 25-meter zeroing bay. The Army uses a 25-meter zero with a ballistic offset that produces a far zero around 300 meters. This lets soldiers zero in a small space and be roughly on target at engagement distances. The USMC uses a similar concept but at 36 yards for a flatter trajectory.

Is this calculator accurate for my specific ammunition?

The calculator uses published ballistic data for common factory loads at standard atmospheric conditions (59°F, sea level). Your actual trajectory will vary with altitude, temperature, barrel length, and specific ammunition lot. The recommendations are accurate within 1-2 inches at typical engagement distances but should be confirmed at the range.

How accurate are the holdover values?

The holdover table is computed from pre-computed ballistic drop data validated against 32 published reference data points from sources including Federal Premium, Fenix Ammunition, Eagle Eye Ammo, and U.S. Army ballistic research. Values are accurate within 1-2 inches at standard atmospheric conditions. Always confirm your zero at the range.

Can I use this for handgun red dots?

This calculator is designed for rifle calibers. Handgun ballistics have significantly different trajectories due to shorter barrels and lower velocities. The height over bore values and ammunition presets in this tool are calibrated for rifle platforms.

Related Resources

• How to Zero a Red Dot Scope in Under 20 Rounds
• What Is MOA on a Red Dot Sight?
• What Is an LPVO? The AR-15 Optic That Does Everything
• How to Zero M4 Iron Sights
• AR-15 Laws by State: 2026 Interactive Map

Last updated: March 2026. Trajectory data validated against published ballistic tables from Federal, Fenix Ammunition, Eagle Eye Ammo, Sniper’s Nest, and U.S. Army TC 3-22.9.