What it measures
Launch angle is the starting climb of the ball, in degrees above level ground, measured just after the ball separates from the face. Zero would be a ball starting perfectly level, and larger numbers mean a steeper start.
It is purely vertical. Left or right start direction is a separate number, launch direction. The meaning is the same for right and left handed golfers.
Typical numbers
PGA Tour players average about 10.4 degrees with the driver and 14.0 degrees with a 6 iron. A tour 7 iron launches a little above 16 degrees, and a full pitching wedge in the mid 20s. LPGA Tour players launch higher, about 12.6 degrees with the driver and 16.7 with a 6 iron, because higher launch helps a slower ball stay in the air.
Everyday golfers average roughly 11 to 13 degrees with the driver. Ideal launch is about 13.6 degrees for a 94 mph driver swing with a level attack angle, about 17 degrees for an 80 mph 6 iron and about 27 degrees for a 72 mph pitching wedge. The best launch depends on club speed and spin, so slower swings generally need more launch.
What changes it
Dynamic loft is the main control. The ball always launches a bit lower than the delivered loft, about 80 percent of it with a driver and nearer 70 percent with mid irons on tour averages. Anything that changes delivered loft, such as shaft lean, a high or low strike on the face, or an open or closed face, changes launch.
Attack angle has a smaller, secondary effect. With the same loft, hitting up adds a little launch, hitting down removes a little. Strike quality matters: thin shots off the lower face of an iron launch lower, high strikes on a driver launch higher with less spin.
What it changes
Launch angle, ball speed and spin rate together decide peak height, carry and landing angle. Too low and the ball does not stay up long enough to carry; too high and it spends its energy climbing and lands short. The ideal is a balance: low spin shots need higher launch, high spin shots need lower launch.
With irons and wedges, launch also affects how steeply the ball lands and how quickly it stops. With the driver, a higher launch paired with lower spin is usually the most efficient way to gain carry at the same speed.
How to use it
Always read launch angle next to spin rate and ball speed. With the driver, if launch is low and spin is high, look for ways to hit up and strike higher on the face. If launch is high and spin is also high, the problem is usually too much loft delivered. With irons, a steady launch from shot to shot is a strong sign of consistent shaft lean and contact.
Bay drill: pick a target launch window for one club, for example 15 to 18 degrees for a 7 iron, and hit ten shots trying to keep every one inside it. Use the shot lab to see how a couple of degrees of launch moves apex and carry at your spin and speed.