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 − gIt 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.
G1 versus G7 ballistic coefficients
Almost all factory ammunition boxes list a G1 BC, referenced to a flat-based spherical-nosed drag model. This calculator uses G1, which is the standard for most hunting and sporting rifle data. G7 is an alternative drag model based on a boat-tail spitzer shape that better matches modern long-range rifle bullets, particularly those with high BC and very low drag. G7 BCs for the same bullet are numerically much lower than G1 BCs (roughly 0.5 times), but when applied to the correct G7 drag curve they produce the same trajectory.
If you only have a G7 BC, multiply it by approximately 2.0 to get a rough G1 equivalent for use in this calculator, then verify the result against a factory drop table if one is available. For most hunting and mid-range shooting purposes, the difference between accurate G1 and G7 modelling is small; it matters most at 800+ yards where drag divergence from the reference model accumulates.
Understanding the zero-range effect
Your zero range determines where the bullet’s path crosses the line of sight. With a 100-yard zero, the bullet rises above the line of sight out to roughly 50–60 yards before falling back through at 100 yards, then dropping below continuously. This means a target at 200 yards is already below the line of sight by several inches. Changing to a 200-yard zero shifts the entire trajectory up, keeping the bullet closer to the line of sight at intermediate ranges — the common “maximum point-blank range” concept where you aim to stay within a kill-zone radius (for example, 3 inches above or below aim) out to maximum distance without hold-over.
Practical table reading
The drop column in the output shows how far the bullet is below the line of sight at each distance when zeroed at your chosen range. To convert drop to scope clicks: most modern scopes adjust in 0.25 MOA or 0.1 MRAD increments per click. One MOA equals approximately 1.047 inches at 100 yards; 1 MRAD equals approximately 3.6 inches at 100 yards. At 500 yards, one MOA equals about 5.2 inches and one MRAD equals about 17.9 inches. Divide the drop in inches by the value-per-click to get the number of elevation clicks needed.
Wind drift is handled the same way: divide the drift in inches by the per-click angular value at the target range to get windage clicks. Always err toward a “cold bore” first shot confirmation when conditions allow — calculated dope and real-world dope diverge most on the first shot from a clean barrel.