Definition
A circle of competence is the domain in which you have real, tested knowledge — where you understand the rules, the typical outcomes, and the ways things go wrong. Inside the circle, your judgment is reliable. Outside it, you are guessing, even if you feel confident.
The size of the circle matters far less than knowing its edges. A small circle you have mapped honestly is more valuable than a large one whose boundary you cannot see, because the danger lies in operating outside your competence without realizing it.
Why it matters
How it works
You map your circle by tracking outcomes honestly: where do your predictions hold, and where are you regularly surprised? Real competence shows up as a track record, not a feeling. To expand the circle, study in earnest and seek feedback that tells you the truth.
When a decision falls outside the circle, the disciplined move is to recognize that, then either build the knowledge first, consult someone who has it, or decline the decision entirely.