My daughter could sit up from just before she turned 5 months but as candymycandy said they’re all different. My little one rolled at 3 months, sat up at nearly 5, crawled at 6 months could pull to standing a few weeks later cruising at 8 months and walked at 9. She was very quick. I have friends who’s babies that are 1& months and still not walking. They’re all so very different.