computedeez
computedeez.com2026-10-08

Zero Calculator

Pick a zero distance and see where the bullet sits against your line of sight at every range, how far the wind moves it, and the holds in inches, MOA and mils.

Zero
50 yd
5.8 MOA above the bore
Highest
+2.1 in
at 144 yd
Point-blank
257 yd zero
inside 6" out to 296 yd
At 500 yd
−46.0 in
1,486 ft/s, 270 ft·lb
The load
The sight
Conditions
Load
5.56x45mm NATO, Federal American Eagle Rifle 55 gr Full Metal Jacket Boat-Tail: G1 0.246, 3,165 ft/s from a 16" barrel
Sight
2.60" above the bore, zeroed at 50 yd
Conditions
10 mph wind from 90°, 0 ft, 59 °F, 0% humidity

Wind drift assumes the same wind all the way to the target, which it rarely is.

The bullet's path

drag the zero line to move the zero
Against the line of sight
-50-39-27-16-470100200300400500yardsinches from line of sight6" targetline of sightzero 50 yd

Point at the chart to read a distance.

Point of impact

Point of aim at the center
1 ft squares25250400500

Point at a mark to read it.

Holds

positive is high or right; negative is low or left
YardsDrop (in)Wind (in)ft/sft·lbSeconds
25−1.2−0.13,0621,1450.024
500.0−0.32,9611,0700.049
100+1.6−1.22,7669340.101
150+2.1−2.72,5808130.158
200+1.2−5.02,4017040.218
250−1.1−8.02,2296070.283
300−5.2−12.02,0645200.353
400−19.9−23.11,7573770.510
500−46.0−39.11,4862700.696

How this is worked out

The bullet is flown, a fraction of a millisecond at a time, from the muzzle to the range you ask for. Two things act on it: gravity, and air drag. Drag comes from the standard G1 or G7 drag curve, which gives the drag on a standard bullet at every speed, scaled by the ballistic coefficient of the bullet you chose. That is exactly what a ballistic coefficient means: how much less this bullet slows than the standard one. Air density comes from the altitude, temperature and humidity you give, through the standard atmosphere.

The line of sight runs from the center of your sight, straight out. The bore sits below it by the sight height and is tilted up until the bullet crosses the line of sight at the zero distance; that tilt is found by trying angles until one lands. Everything in the table is measured against that line: positive is above or to the right of where you aimed, negative below or to the left. In the example on this page, a 55 gr bullet at 3,165 ft/s with a 2.6" sight, zeroed at 50 yards, rises to 2.1" high at 144 yards and is 5.2" low at 300.

Wind is applied as the air moving past the bullet, so a crosswind pushes it sideways for the whole flight and a headwind slows it slightly. The point-blank zero is found by tilting the bore until the bullet's highest point is half the target size above the line of sight; it then stays inside the target from the muzzle until it has fallen half the target size below, and that distance is the point-blank range.

How to use it

  1. Pick your cartridge and the load you shoot. The ballistic coefficient, velocity and weight fill in from the maker's published figures. If you have a chronograph reading, type it over the velocity.
  2. Set the barrel length. The library velocity is adjusted from the maker's test barrel by a published per-inch rule, and the adjustment is shown so you can judge it.
  3. Set the sight height: the center of the scope tube or red dot above the center of the bore. Around 1.5" for a scope on a bolt gun, 2.5" to 2.9" for an optic on an AR, half an inch or so for pistol sights.
  4. Choose a zero. Use a preset, drag the line on the chart, or tappoint-blank for the zero that keeps the bullet inside your target for the greatest distance.
  5. Read the holds at the distances you shoot, in inches, MOA or mils, and print the sheet to take to the range.

What it assumes

  • A point-mass model: the bullet is a point under gravity and drag, with drag from the standard G1 or G7 drag function scaled by the ballistic coefficient. This is what a published ballistic coefficient means, and it is the model behind every ballistic calculator short of a measured drag curve for one bullet.
  • Ballistic coefficients are taken as referenced to the ICAO standard atmosphere at sea level (59 °F, 29.92 inHg, dry), which is how they are published today.
  • The shot is level. Spin drift, Coriolis and the incline of the shot are not modeled; each is worth about a minute of angle at a thousand yards.
  • The wind is the same speed and direction all the way to the target.
  • Manufacturers measure velocity in a test barrel, usually a long one, and their ballistic coefficients are sometimes generous. A chronograph reading from your own rifle is better than the box.

Sources

The load library: 263 loads across 41 cartridges, every figure read from the maker's own page. 129 pages, listed here.