it varies- you will be able to tell in a week or two and I don't think there is any way around it- even at that, as the child gets older it all changes again- what age child is he?
Generally age 2- 2 hours after lunch, then to bed around 8pm- up at 7am-----but it could vary- sometimes they get a 30 minute nap and still aren't too sleepy at bedtime.
Some kiddos at age 2 don't take naps-
age 3-5 anywhere from one hour after lunch to no nap- but they should be able to sooth themselves and rest for at least 30 minutes quietly- hopefully- if not you can give them a book to look at quietly if they promise not to make any noise.
The most important part is the structured timing-
8:30-9:30 outside supervised play
9:30-11:00:00 diaper check, snack, free play maybe in play pen if he is that young
11:00-12:00 story and cuddle one on one time, maybe music video sing alongs
12:00-12:30 meal and diaper check
12:45 -2:00 story and nap
No they can't read a clock but they read the consistent schedules you set before them- after they eat and hear their story, they just realize nap is next if you stay with a good routine. Sorry if you knew all that already....
***outside play (sometimes this helps them want a nap too, it wears them out but not always)
bottom line- just have to learn your own child and follow their signals sometimes