Ballistic Calculator

How well your bullet holds its speed. Printed on the box or the bullet maker's site.

The ballistic coefficient compares your bullet's drag with a standard reference shape. A higher BC loses speed more slowly, so it drops and drifts less. Use the number the bullet maker publishes, and note whether it is a G1 or a G7 figure: the same bullet has two very different numbers.

Which reference shape the BC is measured against. Pick the one your BC is quoted in.

G1 is an old flat-based reference shape; G7 is a long boat-tail shape much closer to modern long-range bullets. A G7 BC is roughly half the G1 number for the same bullet. Either works here, because each is solved with its own drag table, but the BC and the setting must match.

How fast the bullet leaves your barrel, in feet per second. A chronograph reading beats the box.

Muzzle velocity has more effect on long-range elevation than anything else you enter. The number on an ammunition box is from the maker's test barrel, which is often longer than yours; a chronograph reading from your own rifle is far better. Without one, expect the table to need truing at distance.

Start from the speed printed on the ammunition box, adjusted for your barrel length.

Ammunition boxes and makers' sites give a velocity and the barrel length it was measured in. A shorter barrel is usually slower and a longer one faster; about 25 fps per inch is a common rule of thumb for standard rifle cartridges and about 40 for magnums. It is only a starting place: box figures are often optimistic, so check your holds at 300 to 500 yards.

A rough BC from your bullet's diameter, weight and shape, when the real one isn't known.

Heavier bullets for their diameter, and sleeker shapes, keep their speed better. From diameter, weight and the shape you pick, this estimates a G7 BC and a range around it. Real bullets of the same shape still differ, so use the published BC whenever you can find it, and treat the estimate as a starting place.

The distance at which your sights and the bullet meet. Holds are measured from here.

The distance your rifle is zeroed at. Every hold in the table is the change from that zero, so a 100-yard zero reads 0 at 100 yards.

Center of the scope above the center of the bore, in inches.

How far the center of your optic sits above the center of the bore. It matters most up close: it is why a rifle shoots low at very short range, and why some zeros cross the sight line twice. Measure it, or use the preset closest to your setup.

Air temperature. Colder air is denser and slows the bullet more.

Air temperature at the range, in degrees Fahrenheit. It changes air density. It does not model the change in your powder's velocity with temperature; enter a muzzle velocity measured in similar conditions for that.

Height above sea level. Thinner air at altitude means less drop.

Your elevation above sea level in feet, used with temperature to estimate air density through a standard atmosphere. If you have a station pressure or density-altitude reading, the closer your inputs are to it, the better.

Wind speed straight across the bullet's path, in miles per hour.

A full-value wind at 90 degrees to the line of fire. For a wind at an angle, enter only the part that blows across: about half the speed for a wind at 30 degrees off the line, about 87% at 60 degrees.

Match your scope's turrets and reticle.

Angular units for holds and turret adjustments. One mil is 3.6 inches at 100 yards; one MOA here is a true minute of angle, 1.047 inches at 100 yards. Use whichever your scope's turrets are marked in.

How far to dial up (or hold over) at that distance, from your zero.

The correction needed at each distance, measured from your zero, in your chosen unit. Dial it on the elevation turret, or hold it on the reticle. The inches column is how far below your point of aim the bullet would land without it.

How far off each elevation could be, given how sure your velocity and BC are.

The table is only as good as its inputs. The likely range reruns it with your velocity 100 fps slower and faster (unless you measured it with a chronograph or trued it to your impacts) and your BC across its range (5% either way for a published BC, wider for an estimate). Close in, the range is small and guesses are fine; it grows quickly with distance, which is where measuring pays off.

Adjusting the inputs until the table matches where your bullets actually hit.

Shoot at a known distance, ideally 400 to 600 yards, and note the elevation that actually centers your group. If it differs from the table, adjust the muzzle velocity until the table agrees, then check a second distance. A trued table beats any estimate, and it is how shooters without a chronograph get good long-range data. The “True it to your impacts” helper does the adjusting for you: give it one distance and the elevation that worked, and it solves for the velocity. The result fits your rifle with the BC you entered, so change the BC and you should true it again.

How far to hold or dial into the wind you entered.

The correction for the crosswind you entered, in your chosen unit and in inches. Hold into the wind.

The bullet's remaining speed at that distance.

How fast the bullet is still traveling at each distance, in feet per second.

Speed as a multiple of the speed of sound in that air.

The bullet's speed divided by the speed of sound at your temperature. Above about Mach 1.2 the bullet is comfortably supersonic.

Near the speed of sound, where predictions become much less certain.

As a bullet slows toward the speed of sound, its drag changes sharply and it can lose stability. Every calculator, this one included, becomes less reliable there. Rows at or below Mach 1.2 are marked: treat them as a starting point to confirm with live fire, not a dial-and-send number.

Seconds from the muzzle to that distance.

How long the bullet takes to reach each distance. Longer flight times mean more wind drift and more lead on a moving target.