7-iron tee height.
¼ inch ball-bottom on a Par 3.
The short answer
¼ inch (6.4 mm) ball-bottom. The lowest tee in the pack.
The 7-iron is the club everyone measures with
The 7-iron is the default club for club fittings, for gapping sessions, for swing-speed benchmarks and for almost every distance conversation golfers have with each other. If one club in your bag deserves a repeatable lie, it is this one, because more of your decisions get anchored to its numbers than to any other club's.
That is the argument for a fixed tee height in one sentence: the club you use as your reference should not be sitting at a different height on every swing.
Why a quarter inch
A 7-iron is meant to be struck with a descending blow, with the low point of the arc ahead of the ball. The tee is not there to help the ball into the air. It is there as insurance against the club reaching the mat before it reaches the ball, which on a mat produces a misleadingly acceptable result rather than an obvious mistake.
What a mat does to a fat 7-iron
On grass, a strike an inch behind the ball digs in, takes turf, and comes up clearly short. On a mat the dense rubber beneath the pile resists, the sole skids forward, and the club still reaches the ball with enough speed to send it a respectable distance. You get a number you believe and a strike you should not. Over a winter of indoor practice that adds up to a swing that works on a mat and not on grass.
Keeping simulator numbers honest
If you are logging carry distances to build a yardage book, three things have to stay fixed between sessions: the ball, the mat, and the lie. The first two are easy to keep constant. The lie is the one that silently drifts, because a pushed-in tee sits lower after a few swings and a rubber tee sits at whatever height the last person left it. A tee that returns to the same height every time removes the variable you are least likely to notice.
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The quarter inch carries down from the 5-iron. From the 9-iron onward, play it flush.
How high should a 7-iron be teed on a mat?
A quarter inch of ball-bottom, about 6.4 mm. Just enough that the club cannot reach the mat before the ball.
Does tee height affect 7-iron carry distance on a simulator?
Yes. A higher tee adds dynamic loft and lowers spin, which usually raises launch and reduces carry. If you are comparing sessions, an inconsistent tee height will show up as inconsistent distance.
Should I tee a 7-iron at all when practising?
On a hitting mat, a low tee is the more honest option, because a mat turns a fat strike into a bounce instead of a divot and hides the error.