I found a formula for wind in forums months ago that works well for me. If it's a tailwind you subtract, a head-wind, you add. 5mph.= + - 2% dth, 7mph.- 3% dth, , 10mph.- 4% dth, 12mph. - 5% dth, 15mph. - 6% dth, 17mph. - 7 dth , 20mph. - 8% dth.... You still need to take into account after the wind configuration, elevations and rough.