Ballistic Coefficient Calculator

Ballistic Coefficient is a number that describes how efficiently a projectile overcomes air resistance during flight. A higher BC means the bullet retains velocity better, resulting in a flatter trajectory, less wind drift, and more energy at the target. BCs typically range from around 0.1 for blunt pistol bullets to over 0.7 for long, sleek rifle bullets.

There are two common methods. The form-factor model uses BC = m / (i × d²), where m is mass in kg, i is the form factor (shape coefficient), and d is the diameter in meters. The drag-coefficient model uses BC = m / (Cd × A), where Cd is the aerodynamic drag coefficient and A is the frontal cross-sectional area (π × d² / 4).

Not always. Calculated BCs based on shape presets and simple formulas are useful approximations, but manufacturers derive BCs from live-fire testing over measured distances using Doppler radar or chronographs. For long-range shooting beyond 400–500 yards, always use the manufacturer's published BC for best accuracy.

Air drag behaves differently across subsonic, transonic, and supersonic flight regimes. The G1 and G7 drag models each assume a specific reference projectile shape, and real bullets deviate from these at different velocities. That's why many manufacturers publish multiple BCs at different velocity ranges — the BC is essentially an average fit for a given speed window.

The form factor i quantifies how a bullet's drag compares to a standard reference projectile. A value of 1.0 means the bullet behaves exactly like the reference; lower values indicate less drag (more aerodynamic), while higher values indicate more drag. Boattail spitzer bullets typically have i values near 1.0, while round-nose bullets may be 1.5 or higher.

G1 and G7 refer to different standard drag models. G1 uses a flat-based, blunt-nosed reference bullet and is traditional for handgun and older rifle data. G7 uses a long, boat-tailed reference that better matches modern long-range rifle bullets. G7 BCs are numerically smaller but more consistent across velocities for high-BC rifle projectiles.

A higher BC means the bullet loses velocity more slowly, so it drops less over a given distance and is pushed less by crosswind. For example, a bullet with BC 0.5 will have significantly less drop at 500 yards than one with BC 0.3 fired at the same muzzle velocity. This is why competitive long-range shooters prioritize high-BC bullets.

This calculator accepts mass in grains, grams, or kilograms, and diameter in inches, centimeters, or meters — all converted internally to SI units (kg and meters) for calculation. For most rifle and handgun applications, entering bullet weight in grains and diameter in inches (e.g. 0.308 for a .30 caliber bullet) is the most practical approach.