Van, you have to pay very close attention to the area the ball will be landing on. A 13 yard pitch landing on a downslope could roll out 16 yds. The same swing landing on an upslope may only go 12. Spin on chips will have little impact, perhaps slightly more on pitches. For greenside pitches, on fairway or light rough I will hit it 1-2 yards lower than the distance. 30-40% I will play just a hair under the actual distance, and 40-50% rough I will add 1 yard generally.