I'm no expert....but have taken a long range shooting course...Windage is all about the ability to "Read" the wind and estimate its speed. Also having the ability to gauge whether it is full value ( blowing 90 degress from one side to another ), half value, quarter value etc. We were taught to watch heat waves in the distance.. through the scope...assess movement of trees and tall grass etc. At the range...you can put out range flags to read the wind and estimate how fast it is.
If there is a formula...that would be great....but I suspect it's a learned ability to read the environment around you at the time. Also...your windage adjustments will vary just as your elevation does...for every caliber and load. Invest in a quality program to plug your data into....and you'll get quality "Dope" or data that you can use to make your adjustments. I use a program called ExBal....and the thing is scary accurate..as long as the information I plug into is as accurate.
This will increase your knowledge base and if used will help you win if you compete or just hit what you are aiming at. One thing most folks are clueless about is reading Mirage ---- Understand it and the "wind is your friend"...
Thanks dirtball and BossHoss. I found how to calculate the wind up to 500 yds. but couldn't find the range factors from 600 to 1000 yds. But I just came up with another question. Coming up with the elevation range factor, a shooter can use the factor of 5.5 for 550 yds. Can I use 7.5 range factor in the formula for 750 yds. in the windage equation? Or does it have to be 7.0?