This adjustment works for straight at you, or straight away from you. For crosswind's experiment taking a little less depending on the direction, you may need a calculator... lol.
5mph= 2%, 7mph= 3%, 10mph= 4%, 12mph=5%, 15mph=6%, 17mph=7%, 20mph=8%
Example's:
150 yards into a 20mph headwind is (150+8% = 162 )
150 yards into a 20mph tailwind is (150-8% = 138 )