2.75 - 4.00”… but it depends on the knife build. My favorite fixed blade is the Grohmann Canadian Belt Knife. Its blade feels “smaller” than its 4” would suggest. Probably because it’s design encourages one to choke up on it. Other knives (like an Ingram) I prefer a 3.25” blade.

“Perfection is Achieved Not When There Is Nothing More to Add, But When There Is Nothing Left to Take Away” Antoine de Saint-Exupery