I did it by eye

Hi everyone,
I'm trying to find an expression that is really useful in Italian, but I don't know what's the equivalent in English. We say "by eye" (ITA: a occhio), is there something similar in English? It is used when you want to say that you do something without many calculations, tools or instruments, you just rely on your skills.

So if have to make a hole in the middle of a circle without taking any measurements, you make it "by eye", relying on what you see, your instinct and your skills. If you have make a cake but you don't have the recipe, you don't know how much flour and sugar you have to use, but if you are skilled enough you can "go by eye", your eye will tell you if the quantities are more or less ok. If draw a circle by hand, you also do it "by eye" because you have no tools to check whether it's ok or not, so it might seem ok "by eye".

Hope you understand, thank you in advance

The idiom 'play it by ear' is also used in the very general sense of 'do something without a plan'...