What model does this calculator use?

It runs a point-mass numerical integration with the standard G1 drag function, stepping the trajectory forward in tiny time increments under gravity and aerodynamic drag. The launch angle is solved so the path crosses the line of sight at your chosen zero range.

What is the ballistic coefficient?

The ballistic coefficient (BC) measures how well a bullet retains velocity against air resistance, referenced to a standard projectile shape. This calculator uses the G1 reference, which is printed on most factory ammunition and bullet boxes. A higher BC means less drop and drift.

How does wind drift work?

Drift is computed from the crosswind component using the classic lag-time relationship: drift equals the crosswind speed multiplied by the difference between actual time of flight and the time the bullet would take in a vacuum. A 90-degree wind gives full effect; a headwind or tailwind gives none.

Why does my real drop differ from the table?

The model assumes a standard sea-level atmosphere. Altitude, temperature, humidity, barrel-to-barrel velocity variation, and your specific lot of ammunition all shift the real trajectory. Always confirm your dope with live fire before relying on it in the field.

What sight height should I enter?

Sight height is the vertical distance from the centre of the bore to the centre of the scope, typically 1.5 to 2.0 inches for a bolt rifle. It mainly affects the very near trajectory and where the bullet first crosses the line of sight.

Bullet Drop Ballistics Calculator

The bullet drop ballistics calculator predicts how far a rifle bullet falls and drifts across its flight path, so you can dial or hold for distance and wind. It models the trajectory with the standard G1 drag function used by virtually all factory ammunition.

How it works

The calculator integrates the bullet’s path as a point mass. At each tiny time step it computes the aerodynamic retardation from the G1 drag coefficient (which varies with Mach number) and your bullet’s ballistic coefficient, then applies gravity:

a_drag = K · Cd(Mach) · v² / BC
a_vertical = a_drag_y − g

It first solves the launch angle by bisection so the bullet crosses your line of sight exactly at the zero range. Then it reports, at each output distance, the drop below line of sight, the wind drift from the crosswind lag time, the remaining velocity, and the time of flight.

Example and notes

A .308 Winchester firing a 168 gr bullet (G1 BC ~0.45) at 2700 fps, zeroed at 100 yards, drops roughly 13 inches at 300 yards and around 50 inches at 500 yards — matching published factory tables closely. A 10 mph full-value crosswind pushes that bullet several inches at 300 yards and over a foot at 500. Because the model uses a standard sea-level atmosphere, treat the output as a starting point: verify your actual come-ups with live fire at distance, especially at high altitude or in extreme temperatures.