When is it a good age/time to put my daughter in a "big girl" bed?

Big bed: She is ready for a big bed once she tries to climb out of her crib somewhere between 12-18 months.

If she falls asleep: on her own in her own room at a consistent bedtime after cuddling, reading & brushing her teeth, sleeps through the night, is not toilet-training or experiencing a major life-change & shows interest in having a " big-girl bed", try it between 18 mos.-3 yrs. Some parents put the mattress on the floor at first. She can use her crib blanket & stuffed animals to make her own "nest." Good luck!