How do professional golfers determine their iron distances?

[The Recreational Golfer]

I hit my stock 7-iron about 155 yards. I know it’s comfortably over 150, and but not close to 160, so I split the difference.

If I were a professional golfer (setting aside the fact that I would be hitting a 7-iron a lot farther than 155 yards), I would know that I hit it 156 or 153, not “about” 155. And yes, there is the consistency issue, but let's set that aside, too.

My question is, how to professional golfers determine the stock distance they hit each club? What is the process they go through?

I’m not asking how you do it, unless you’re a professional, or how you think they do it. I want to know how the pros really do it, so readers of this forum can do the same thing.

[michaeljames92]

Until recently, with trackman giving more or less exact distances, they just found them with trial and error over a period of time.

[Shorty]

Ever heard of measurement? How else do you think they do it? It s no more complex or simple than that.

[GaijinGolfer]

Trackman and putting in their time at the range.