Asking the question is awkward for five seconds. Guessing wrong can be awkward for a week.

The discomfort of not knowing in public is brief and contained. The discomfort of having done the wrong thing confidently is longer, involves other people, and usually requires undoing work. Trading a small immediate awkwardness for a large delayed one is a bad deal that almost everyone takes, because the small one is happening now.

When you notice yourself about to guess, ask instead. Keep it short and specific so it does not become a performance of confusion. Five seconds is the entire price, and it is payable once.