underestimate
🇺🇸
/ˌʌndərˈestɪmeɪt/
🇬🇧
/ˌʌndərˈestɪmeɪt/
to think something is smaller or less than it really is
Don't underestimate how much time this project will take.
to not see how good, strong, or difficult someone or something really is
You should never underestimate your opponent's skill.
a guess that is too low about size, cost, or amount
My estimate of 100 people was a big underestimate of the actual crowd size.