Bullet Wind Drift Calculator

Bullet Wind Drift Calculation

Wind pushes a bullet sideways during flight. The drift depends on:

1. Time of flight: slower bullet = more drift
2. Crosswind component: only the perpendicular wind matters
3. Bullet ballistic coefficient (BC): higher BC = less drift

Simplified field formula (good to ~600 yards for hunting calibers): Drift (inches) ≈ (Wind in mph × Range in 100s × Range in 100s) / (BC × 25)

For more accuracy, modern apps (Strelok, Applied Ballistics) solve the full drag model. This calculator uses the simplified field approximation that hunters can do in their head.

Typical bullet BC values (G1):

Wind angle adjustment (clock method):

Picture the clock face lying flat with 12 o’clock straight down range. Only the crosswind component moves the bullet sideways, and that component is the sine of the angle off the line of fire. Each hour on the face is 30°, which gives four values and no others:

The row that catches people is the 60° one. A 2 o’clock wind feels like a mild quartering breeze and it is worth 87% of full value, not half. Getting that wrong is a 42% error in the correction, which at 400 yards with a .308 is the difference between the middle of the vitals and a gut shot.

So a 10 mph wind at 5 o’clock is 5 mph of effective crosswind, and the same 10 mph at 4 o’clock is 8.7 mph.

Practical drift at 300 yards (with 10 mph full crosswind):

Hunting implications:

• Most ethical hunting shots are under 300 yards: wind drift is manageable
• A 6-inch lateral error at 300 yards can mean a wounded animal
• Practice estimating wind in 5 mph increments: that’s the resolution that matters
• Use trees, grass, mirage to judge wind down-range, not just at the muzzle

Ranging wind by visual cues:

• 0-3 mph: smoke drifts but flag hangs limp
• 3-7 mph: leaves rustle, light flags lift
• 7-12 mph: small branches sway, dust kicks
• 12-18 mph: small trees sway, tall grass bends fully over
• 18-24 mph: large branches move, hard to walk into wind

MOA correction: 1 MOA is 1.047 inches at 100 yards, so 3.14 inches at 300 and 6.28 at 600. Most people round it to an inch in their head and that is fine at hunting range, but the 4.7% adds up: at 600 yards the rounded version is more than an inch off, and this page uses the exact figure so it agrees with the bullet drop calculator when you run the same shot through both.

Mils: 1 mil is 3.438 MOA, or 3.6 inches at 100 yards. Scopes are one or the other, so dial in the unit your turrets are actually marked in and never convert at the rifle.