НА ГЛАЗ (НА ГЛАЗОК) определять, прикидыватьPrepPthese forms onlyadv
(to measure sth. , judge the size of sth.etc) just by looking and approximating, without using any measuring devices: (measure (judge etc) sth. ) by eye
(tell) by looking.
Покупать скот нужен опыт, надо на глаз определить, как откормлена скотина, сколько в ней ценного мяса, сколько жира... (Рыбаков 1). It takes experience to buy animals, you have to be able to judge by eye what the animal has been fed on, how much valuable meat there is on it, and how much fat... (1a).
«Я и так на глаз вижу, сколько там пудов в мешках!» (Искандер 5). "Anyway, I can tell by looking how many pounds there are in the sacks!" (5a).