What age can a baby be carried in a backpack carrier?

I am looking to purchase an Ergo Baby Carrier, it can be worn on the front, hip and as a backpack. My baby is 5 months old and i was wondering if she'd be able to be in it as a backpack.|||Until the baby san sit up on its own its best to carry on the front or hip|||I carried both of my girls in a front carrier until they were a year old. Or I would use the sling and put them on my hip when they were about 8 months. At 5 months, I would not put them on my back.|||if she can sit up by herself and holds her head really well then yeah she'd be fine. if not then id wait a little longer|||As long as she has good head control.|||I dont see why not. im sure your baby is big enough that she will fit in there just fine. :)