How much sleep should a 16 month old be getting during the day

[Saltire]

He goes to bed between 6pm and 6.45 and wakens at 5. He then doesn't sleep very often during the day. Once in a blue moon he'll have an hour, usually 15 minutes and wakens up screaming nad crying and rubbing eyes, pulling hair and very obviously still tired.

It varies so much from child to child but 15 minutes - especially if they still look tired - certainly sounds like it's not enough. An afternoon nap is pretty normal for most children that age.. Have you tried settling him back down when he wakes after 15 mins? Do different environments make a difference?... quiet, noisy, moving etc.

My DD is 16 months

She has around 2 hours sleep in the day and 11 - 12 hours at night

She sleeps around 11.30 - 1.30 pm after her lunch