How much fluids should a 1 year old drink a day?

I'm wondering the same thing, but I'll tell you what my daughter drinks, if it helps, she's just over 13 months, 12 months corrected.

3-6 oz cows milk (we've taken away 2 bottles and replaced them with sippy cups of cows milk)
10-12 oz formula (bottles morning and night still)
3-6 oz water (sometimes with a little juice added)

I'd say it evens out at about 18-20oz of liquids a day, and she's never been constipated. She has 3 meals and a snack during the day, cereal with fruit for breakfast, main meat meal at lunch, and something light for dinner, and usually yoghurt or finger foods for a snack.