when do babies start to sit up

Babies typically start sitting up with support around 4 to 6 months old and can usually sit up independently between 7 to 9 months. Some babies show early signs of readiness as early as 4 months, using their arms for balance in a "tripod" position. By about 6 months, many babies begin sitting with little help, and by 9 months, they tend to sit well without support and can get in and out of a sitting position with some assistance. This milestone depends on good head control and upper body strength, which develop gradually through activities like tummy time.