Afternoon Naps.

depends on the child but I would say between 2-3 hours would be average...maybe even a little longer since it's her only nap...as long as you can still get her to bed at night w/o problems.

My son (22 months) sleeps anywhere from 2.5 - 4 hours during his only nap, depending on the day. He sleeps about 12-13 hours at night.

my daughter at that age also slept only once, was from 2-3 hours, now she's 2,5yo sleeps 2 hours

L.,
My 15 month old still takes a morning nap for 2 to 2.5 hours and then a late afternoon nap for about 1.5 to 2 hours. He sleeps from 7pm - around 6am.
I really think it depends on the child though.

Since my now 23 mos old daughter was a year old and we dropped her to one nap a day, she has been taking one 3-4 hour nap in the afternoons, usually 12-3 or 1-4.

I just had to chime in because I think it definitely depends on the child, but I think 1 to 3 hours is normal. My DD almost never sleeps longer than 2.