Most babies learn to get themselves into a sitting position from lying down between 8 and 12 months old. The CDC lists “gets to a sitting position by herself” as a milestone that 75% or more of babies reach by 9 months. This is a different skill from sitting upright when placed, which typically happens months earlier. You can support this transition with specific activities that build the strength and body awareness your baby needs.
Why This Skill Takes Longer Than Sitting
Babies can usually sit upright when placed in position between 3 and 6 months. But getting into that position independently is a much more complex movement. It requires your baby to roll to one side, push up with their arms, shift their weight, and rotate their trunk, all in a coordinated sequence. That demands core strength, arm strength, and balance working together in a way that younger babies simply haven’t developed yet.
Before a baby can sit up from lying down, they typically need to have checked off several earlier milestones in order: lifting their head 90 degrees during tummy time (0 to 3 months), rolling from back to tummy (3 to 6 months), sitting without support when placed (3 to 6 months), and getting into a hands-and-knees position (6 to 9 months). If your baby hasn’t reached these stages yet, focus on those foundational skills first. The floor-to-sit transition builds on all of them.
How Babies Actually Do It
Adults sit up by crunching forward, but babies don’t have the abdominal strength for that. Instead, they use one of two common patterns. In the first, the baby rolls to one side, props up on one hand, then pushes their upper body upright while swinging their legs around. In the second, the baby gets onto hands and knees first, then rocks back onto their bottom. Both approaches rely heavily on trunk rotation and the ability to shift weight from one side to the other. Understanding these movement patterns helps you know what to practice rather than trying to pull your baby straight up from lying flat, which doesn’t mimic the natural movement at all.
Building Core and Trunk Strength
The most effective starting point is lap sitting. Place your baby on your lap facing outward and notice where you naturally hold them for support. If you’re supporting their chest, they need more trunk strength. If you only need to hold at the waist or pelvis, they’re getting closer to independent sitting. Gradually lower your hand support over days and weeks. This challenges your baby to engage their own trunk muscles to keep their head and body upright, and it happens naturally during everyday holding and play.
Once your baby can stay upright on your lap with support only around the waist, move to floor practice. Place firm cushions or foam blocks (about 10 to 15 centimeters high) on either side of your baby and one behind them. The blocks should touch their thighs and chest on each side. This setup gives them something to prop their hands against if they tip, while still requiring their core muscles to do real work. It’s a safer and more effective approach than propping them in a corner or using a sitting device, which doesn’t build the same active muscle engagement.
Practicing the Side Push-Up
Since babies sit up by pushing from a side-lying position, you can practice this movement pattern directly. Lay your baby on their side on a soft surface. Place one hand gently on their hip to stabilize their lower body, then hold a toy slightly above and in front of them to encourage them to push up with their lower arm. They may only lift their head and shoulders at first. That’s the beginning of the pattern. Over time, they’ll start to push higher and shift their weight onto their hand.
You can also practice this during diaper changes or when getting your baby up from the floor. Instead of lifting them straight up, gently roll them to one side first, then guide them upward from that position. This reinforces the movement sequence they’ll eventually use on their own.
Encouraging Reaching and Rotation
Once your baby can sit upright with the cushion supports, start placing toys within easy reach to one side. Have them reach with one hand, then switch the toy to the other side. This builds the trunk rotation that’s essential for the lying-to-sitting transition. As their balance improves over the following weeks, move toys slightly further away, sometimes forward, sometimes to the side. Reaching further requires your baby to control their center of gravity through a wider range of motion.
Trunk rotation is the piece many parents overlook. A baby who can sit still but never twists or reaches sideways hasn’t developed the rotational control needed to push up from lying down. Floor play where toys are scattered around them, not just placed directly in front, naturally encourages this.
What the Transition to Kneeling Looks Like
As your baby gets stronger, you’ll notice them starting to move out of sitting and into other positions. This typically happens in one of two ways: they lean far forward, put their weight on their hands, and end up on hands and knees, or they rotate their trunk and reach across their body to shift into kneeling. Both of these movements use the same core strength and weight-shifting ability that the sit-up transition requires, so they tend to develop around the same time. Encouraging your baby to move between positions freely on the floor, rather than keeping them in one spot, supports all of these skills together.
Creating a Safe Practice Space
Babies learning to sit up will topple over frequently, often sideways or backward. Practice on a carpeted floor or a firm play mat. Avoid soft surfaces like beds or couches, which make balancing harder and create a fall risk off the edge. Stay within arm’s reach during practice sessions, and keep the area clear of hard or sharp objects. The foam blocks or cushions used for supported sitting also serve as padding if your baby tips to the side.
Keep practice sessions short and playful. A few minutes several times a day is more productive than one long session where your baby gets frustrated or fatigued. Tummy time, rolling games, and reaching for toys during regular play all contribute to the same muscle groups, so structured “sitting practice” is just one piece of the puzzle.
When Progress Seems Slow
There’s a wide normal range for this milestone. Some babies sit up from lying down at 7 months, others not until 12 months. If your baby is hitting other milestones on schedule, like babbling, using their hands to explore objects, and making eye contact, but seems behind only in gross motor skills, this pattern has a name: developmental motor maturation delay. These children typically have slightly low muscle tone but normal strength, and they catch up over time without intervention.
One characteristic sign is what clinicians call the “sitting on air” position: when you hold the baby upright under their arms, they hold their back straight, bend their hips outward, and extend their knees, as if sitting on an invisible chair. Children with this pattern achieve head and arm control on time but are slower to sit, stand, and walk independently. They generally reach all motor milestones eventually, just on a later timeline. If your baby has no other developmental concerns and their pediatrician finds a normal neurological exam, routine imaging or lab tests aren’t typically needed.
Red flags that warrant earlier evaluation include loss of skills your baby previously had, stiffness or rigidity in the limbs, delays across multiple areas (not just movement), or failure to bear any weight on the legs by 9 to 10 months.