길고 짧은 것은 대어 보아야 안다

Literal Meaning

You have to measure it to know if it is too long or too short.

Usage

Used to encourage someone who is unsure if he or she has the ability or skills needed to do a certain task or meet a certain challenge to accept the task or challenge to find out for sure.

Korean Equivalent

잘하고 못하는 것은 실제로 겨루어 보아야 안다.

English Equivalent

You will never know until you try.