When Do Babies Sit Up? What You Need To Know

Sitting up is a monumental rite of passage for baby and their parents. For many, it’s a sign of independence and growing up. My babies were much more content once they could sit on their own. They could look around and observe their surroundings or have their hands free to play with toys. As one of the first major gross motor milestones of development, sitting up is something to encourage and look forward to with baby.¹ You may be eager to get baby sitting up but are unsure when to expect this milestone, specifically what age babies sit up. You might also wonder how to help them achieve it and what to do if they are not quite there when you think they should be. Here, we will dive into all that and more as we answer the question, “When do babies start sitting up on their own?”

So, at what age do babies sit up by themselves? Your baby should be able to sit in a supported seat by 6 months. This may be in a tripod sitting position, in which they hold themselves sitting up by leaning forward on their hands. This could also mean you are supporting them from behind or the sides by holding them up or making sure they do not fall over.²

According to the CDC, your baby should be sitting without support by 9 months. At this age, your baby should also be able to get seated without help.³

In one large study of gross motor development, all the babies achieved sitting without support at around 9 months. The youngest baby to sit without support was just under 4 months old, and the oldest baby to sit was 9 months. The average age of babies in this study who sat without support was 6 months old.¹

Before being able to sit, your baby needs head control and core strength to hold themselves upright. Signs of improving head control and core strength include actions such as:⁴

If your baby has mastered these skills, these may be signs that they are ready to start trying to sit up.

Infant strength develops from the top downward, moving from head to feet. The first form of a baby sitting is the tripod sitting position. In this position, their hands prop them up between their outstretched legs.⁴

Eventually, as posture and strength develop, babies learn to sit without the support of their hands, but they are still working on balance and stability. They often need to catch themselves and may still topple over often.⁴

The final stage of sitting is the most stable — at this point, babies can balance even when twisting, turning the head, and moving the arms.⁴ I remember realizing I was no longer worried about my toddler knocking over my baby from a seated position because she had finally mastered balancing while sitting!

Here are some tips and tricks to help your little one practice sitting.

At my daughter’s four-month appointment, since she was rolling and lifting her head in tummy time, our pediatrician encouraged me to help my baby start sitting. She suggested sitting on the floor behind her with my legs in the shape of a V so she was supported from behind and on the sides. I also placed her hands on the floor so she could learn to support herself in the tripod sitting position.

To provide support, you can also place your baby in a seated position and keep your hands around their torso or ribs to hold them up. They will eventually learn to balance with their core or lean on one or both hands while looking around and playing with toys.²

Before my daughter could sit up without support, I used to sit her up with a C-shaped nursing pillow behind her. I would sit across from her or place toys in front of her, encouraging her to play with me while sitting up and balancing. This encouraged her to sit and gave me peace of mind that she would not fall backward and bump her head on the floor.

I suspect, in some ways, this might have backfired. The pillow began to serve as a safety net — she knew it was there and would intentionally throw herself straight backward onto it from a seated position. I am sure she developed core strength from essentially doing sit-ups off the Boppy pillow, but she had to learn the hard way (by falling backward) that the pillow would not always be there once she learned how to sit and balance without support!

Several studies have demonstrated a positive association between tummy time and faster gross motor development. Babies who practiced more tummy time achieved sitting (both supported and independent), crawling, and pulling to stand at earlier ages.⁵

Exercise and Massage

In cultures that practice infant exercise and massage, babies sit at younger ages on average. Parents are so trusting of their stability that they walk away from their baby when they’re sitting up.⁴

While support from parents can help,  baby sit-up seats do not help a baby learn to sit independently. It may seem counterintuitive, but these baby containers poorly distribute a baby’s weight and place undue pressure on their back and hips. These seats also restrict a baby’s movements and teach them to rely on the support of these “chairs.” Furthermore, being confined to a baby sit-up seat immobilizes a baby’s joints and prevents their muscles from strengthening.⁶

So you have limited your baby’s time in containers, practiced lots of tummy time, provided endless support (literally!), and worked hard to encourage your baby to sit up. Once they have mastered this skill, you probably wonder what might come next. Sitting is usually the next major gross motor milestone after rolling.⁴ It starts the cascade of strength, development, and movement in the first 12 to 18 months of your baby’s life. Once they start sitting, other motor milestones may quickly follow.¹

One study of infant motor development showed that gross motor milestones follow a predictable sequence about 90% of the time. The following milestones to look out for after sitting include:¹

Infant motor milestones after sitting most often occur in the order listed above, but sometimes, crawling and standing with support can be swapped.¹

If your baby is not meeting these milestones or you are concerned, do not hesitate to ask for help. No one knows your baby better than you! Go with your gut and always seek an exam from a trusted provider if you are concerned your baby may not meet gross motor milestones. If your baby was previously meeting a milestone but stopped performing that action, this is also worth investigating.²

Your pediatrician should be able to perform a developmental screening and refer you to a specialist if needed. It is okay to seek a second opinion if your pediatrician is not concerned, but you are still worried. You can also often make an appointment with an infant physical therapist without a referral from a doctor. Finally, you could call your state’s early intervention program for an evaluation and eligibility. Therapy can make a substantial difference, especially when initiated early.²

My second daughter was on the later end of “normal” for sitting and crawling. Her pediatrician assured me she was not concerned but gave me a physical therapy referral anyway. She reminded me that I know my baby best. I was not worried she would never meet these milestones; however, I was interested in pursuing therapy to learn how to better help her achieve these goals and catch up to her peers.

In the time leading up to the appointment, we started practicing more supported sitting and motivation through play. Ironically, she started sitting independently and army crawling just days before her physical therapy appointment, so I canceled it. However, I still remember our pediatrician making me feel heard, supported, and validated.

It can be emotional when your baby starts to sit! They always seem like less of a baby once they start sitting. As bittersweet as your baby learning to sit up may be, it is also an exciting milestone. It enables them to play with toys and see more of the world around them. There is much you can do to encourage sitting, and if you are ever concerned about a developmental delay, your pediatrician is an excellent resource for further assessment. With the right encouragement and interventions, your baby will be sitting (crawling, standing, and walking!) in no time.