“I don’t know, let me find out” has saved more leaders than any confident guess.

Guessing confidently buys you about four minutes and costs you everything downstream if the guess is wrong. Admitting the gap does the opposite, because it tells everyone that when you do say something definite, it can be relied on. People forgive not knowing far more easily than they forgive being confidently misled. The admission also removes the pressure to defend a position you invented under stress.

Say you will find out and then actually find out, with a time attached. Come back with the answer even if nobody chased you. That second half is what makes the first half work.