No real formula, but we no that 1″ in club length can add 1 mph of clubhead speed. 1 mph of clubhead speed translates into 2.3 yards of distance. IF we assume the shaft weights are similar and the flex characteristics are similar, and your fairway wood is 42.5″ (for example) and your hybrid with the same loft is 39.5″, the distance difference just based on the length variable would be 6.9 yards. If the fairway wood shaft is lighter than the hybrid, then that could also add to the difference. A 30 gram shaft weight difference (lighter in the fairway wood) can translate into approximately .7 milliseconds (1.5 mph), which could give you another 3.45 yards. So that would be 9.35 yards. My experience is that other factors like the overall club weight, the difference in spin rate, launch angle differences due to the cg location and attack angle, would make the difference even greater.
I now that’s not exact, but hopefully will give you some kind of idea. Best to get on a launch monitor with a hybrid and fairway wood of the same lofts and simply hit them and see what you get. It can vary from one player to the next.
Very helpful….thanks Brett!