The outside-to-inside swing path and the open clubface combine to make the really big slices. The angle the clubface is open to the swing path is called the Slice Angle. For example, if you have a straight swing and hit a drive with a 3º open clubface (slice angle of 3º) the ball will wind up about 21 yards off-line to the right. This is based on testing done by the Golf Society of Great Britain.

If you hit another drive and your clubface is still at 3º open, but this time your swing is 3º off-line from outside-to-inside, your slice will be double. Your slice angle is 6º, meaning, your clubface is, in total, 6º open from the swing path. This will cause a slice of 42 yards. Because of the outside-to-inside swing path, the ball will take off more to the left so it won’t land a full 42 yards to the right. But, even if the shot starts to the left it may not by playable on a narrow fairway. This is the kind of shot where you aim at the trees on the left and hope the ball doesn’t go into the trees on the right.

You can slice if you have a perfectly straight swing path. Even if you have an inside-to-outside swing path you can still slice. The key is the position of the clubface in relation to the swing path, the slice angle. If your swing path is perfectly straight to the target, but your clubface is open you will slice. If you swing inside-to-outside and your clubface is open to your swing path you will slice (called a push slice). Check the scuff marks on the sole of your clubs. If they are diagonal, they are showing your slice angle.

For example, on a drive, if the angle was 10º (meaning the clubface was open 10º to the swing path), you’re going to have a severe slice, no matter what the swing path. The angle the clubface is open to the swing path determines how much the ball slices. In addition, the greater the speed of the clubface at impact, the greater the spin, therefore the bigger the slice. The biggest hitters hit the biggest slices.