I’ve seen numerous formulas for calculating wind drift in the field, none of which are any good when your brain is boiling prior to a shot. The only workable one comes from my friend and colleague Wayne van Zwoll. According to Wayne, if you’re shooting 180-grain .30/06 bullets at 2,700 fps, and the wind is coming at 10 mph from a right angle, allow 1 inch at 100 yards, 2 inches at 200, 6 inches at 300, and 12 inches at 400. If the wind is coming from 45 degrees instead of 90, you halve these allowances. If it’s blowing 20 mph, you double them.