いくつ

いくつ asks "how many" about things you count with the ～つ numbers: ひとつ一つ, ふたつ二つ, みっつ三つ. It goes where the number would go in the answer, and the question ends in か.

いくつ or 何 + counter

いくつ goes with the ～つ numbers, which count objects that have no counter of their own. People, flat things, long things and the rest have their own counter, and you ask with なん何 plus that counter.

• × 学生はいくついますか → 学生は何人いますか

Asking someone's age

いくつ also asks how old someone is. With お in front, おいくつ is the polite way to ask an adult; なん何さい歳 is more direct.

The answer counts years with とし歳. A small child's age can also be given with the ～つ numbers.