over-estimate

/OW1 V ER0 EH0 S T AH0 M AH0 T/
verb
  1. 1

    To judge or calculate too highly.

    โ€œI overestimated the number of attendees, and bought far too much food for the party.โ€

Source: https://en.wiktionary.org/wiki/over-estimate, https://en.wiktionary.org/wiki/overestimate