No one can tell you how many pills or mgs it would take for you to OD as it depends on the person and many variables. You already know how many percocet you can handke so use that as a comparison. If you get where you want to be with 30 mg of percocet 10mg (oxy + 'x' APAP) then you take 30 mg oxy IR to feel that feeling you are aiming for. Length of notable high was mentioned already, but you should be able to feel for yourself when the high fades. At that point, yes-you could take 10-15mg more (for example) to feel 'better' or.. not sober. Why take much more if you are just going to sleep, anyway? Sounds like you are not addicted or anything so it's not like you need take more to avoid w/ds or anything like that. Why waste the pills-save them for daytime or when you'll be awake to enjoy them.
Just be smart. Search the net on oxy half life and all that jazz to educate yourself a bit so you aren't being careless in your drug use. You can never know too much about things you put into your body. Also, the BA (bioavailability) is higher if you take your oxy orally as opposed to insufflating them. Your high lasts longer if taken orally, you get more out of the pill/s (waste less... you don't get all the active ingredients when snorting). If you snort it kicks in fastee but you lose some of it and the high is shorter. Hope this info helps a little. Lmk if you want more info. There are maaaany threads on there related to oxy, so look around if you have dome timd. Go to the OD (other drugs) directory, threads of importance I think? Then find 'oxycodone', and go from there. I have used those/that thread often for reference back in the day. zalso, you can try potentiating the oxy: you'll use less and stretch out your stash as well as intensify the experience.