Not what they say to your face, what they say when there's no reason to be polite about it. That's the closest thing to an honest measure of the reputation you're actually building, one interaction at a time.
Most people think about their reputation the way they think about a résumé, a set of accomplishments they can point to and describe. Reputation doesn't actually work that way. It's built almost entirely out of small, often unremarkable moments that nobody's keeping score of individually: how you handled a disagreement in a meeting three months ago, whether you followed up on something you said you would, how you treated someone who couldn't do anything for your career. None of those moments feel significant while they're happening. Collectively, they're the entire thing.
You don't get to write your own reputation directly. You can only control the raw material it's built from.
This is worth taking seriously because you don't get to write your own reputation directly, you can only control the raw material it's built from. If you're consistently calm under pressure, people will describe you as someone who creates calm, without you ever having claimed that about yourself. If you're consistently the one who tells the truth even when it's inconvenient, that becomes the sentence people reach for when your name comes up, unprompted.
Imagine a colleague describing you to someone who's never met you, with no reason to flatter or criticize, just an honest, offhand answer to "what are they like to work with?" Whatever sentence comes to mind, that's a rough approximation of your current reputation. If it's not what you'd want it to be, the gap tells you exactly what to work on, not in some abstract sense, but in the next few real interactions you have.
A handful of qualities tend to show up disproportionately often in the reputations people actually want: someone who creates calm instead of adding to the noise in a stressful moment. Someone who solves problems rather than just describing them. Someone who tells the truth, even the version that's slightly uncomfortable to say. Someone who follows through without needing to be reminded. And someone who makes the people around them better, not just their own results. None of these require talent in the traditional sense. They're all built from repeated choices, available to anyone regardless of role or title.
The uncomfortable part of this is that reputation moves slowly to build and quickly to damage, a single bad moment, handled poorly, can undo a longer stretch of good ones, at least in the short term. That's not a reason to be paralyzed by every interaction. It's a reason to think of your reputation less as a project you finish and more as something you're quietly renewing, or eroding, in every ordinary conversation you have.