At anywhere near 100kt,
max drift = half the wind (i.e. 20kt wind -> 10 degree offset)
At anywhere near 150kt
max drift = 1/3 of the wind
The above work for a wide range of angles; much wider that most people think. The truth is that nobody (not having an air data computer plus a GPS) really knows what the wind aloft is, accurately enough to make a difference. If you can sort out your heading within 5 degrees, that's just fine. If you have time, you can improve on it as you go along. If you haven't got time (like on an instrument approach) you have other more important things to do anyway.