Babies will almost certainly learn to sit independently between the 4 and 7 months. This is about the same time that will have rolling over and holding his head up. Most babies can sit well for several minutes without support by the time they’re 8 months old.
Babies sit independently gives a new perspective on the world. Once his back and neck muscles are strong enough to hold him upright and he’s figured out where to put his legs so he won’t topple over, it’s just a matter of time until he moves on to crawling, standing, and walking. Most babies can sit well for several minutes without support by the time they’re 8 months old.
Starting at 4 months, babies’ neck and head muscles strengthen quickly, and the baby will learn to raise and hold his head up while the baby lying on the stomach and him/her up on arms and hold his chest off the ground, sort of a mini-pushup. By 5 months the babies may be able to sit for a moment without support, though you should stay nearby to provide support and encircle the babies with pillows to cushion a possible fall down.
Almost immediately the baby will build up how to maintain his balance while sitting by leaning forward on one or both arms in a support position. By 7 months the babies probably are able to sit with out supported and the baby will learn how to turn to reach a preferred object while sitting. At the 8 months old the babies are capable to sit without any support. At the end of the 9 months the babies crawl. Exact at 10 months the babies will crawl and sitting with out support.