Most milestone charts you'll see online are some version of "by 6 months your baby should be doing X." The "should be" framing is a problem. Babies hit skills across a wide range of ages, and the older charts were often based on the average age, which by definition meant half of all babies were "behind."
The CDC updated its milestones in 2022 to use a different standard: skills that 75% of babies have by a given age. This is more realistic and a lot more useful. If your baby hasn't done something by the listed age, they're in the bottom quarter for that skill, which is a good moment to mention it at a checkup. Not a moment to panic.
Here's a practical month-by-month guide using that framework, with the CDC's checklists by age as the reference point.
The big table
| Age | Most babies are doing |
|---|---|
| 1 month | Lifting head briefly during tummy time, looking at faces, making sounds other than crying |
| 2 months | Smiling at people, holding head up while on tummy, cooing and gurgling |
| 4 months | Holding head steady without support, pushing up on forearms during tummy time, laughing, turning head toward sounds |
| 6 months | Rolling both ways (back to belly takes longer than belly to back), reaching for toys, putting things in their mouth, making blowing or "raspberry" sounds |
| 9 months | Sitting without support, getting into a sitting position, looking for dropped objects, babbling with consonants ("baba," "mama" without meaning) |
| 12 months | Pulling up to stand, cruising along furniture, waving, playing pat-a-cake or peekaboo, saying one word with meaning, picking up small things with thumb and forefinger |
| 15 months | Taking a few steps, using 1 to 3 words besides "mama" and "dada," following simple instructions like "give me the toy" |
| 18 months | Walking confidently, scribbling, drinking from a cup, pointing to ask for things |
These are 75th-percentile-ish targets. Plenty of babies do things earlier. Some do them later and are still fine.
Month by month, in plain terms
0 to 1 month
The first month is mostly about feeding, sleeping, and adjusting to being outside. Babies make eye contact, react to voices and faces, and turn toward light or movement. By the end of the first month, most can lift their head briefly during tummy time.
You won't see much that feels like "developing skills" yet. That's normal. The brain is doing a huge amount of work invisibly.
2 months
The first social smile is the headline. Around 6 to 8 weeks, your baby starts smiling in response to you, not just in their sleep. They start cooing, making vowel sounds, and watching faces with real interest.
Tummy time should be daily by now, in short bouts. Most 2-month-olds can hold their head up briefly while on their belly.
3 to 4 months
This is when babies start feeling like little people. They laugh out loud (often at things you don't think are funny), hold their head steady when supported sitting, push up on their forearms, and start reaching for objects. Many roll from belly to back around 4 months.
The 4-month mark is also when sleep often gets harder for a few weeks (see the 4-month regression). The two are unrelated developmentally; they just often coincide.
5 to 6 months
The big shifts: rolling both ways, sitting with support, reaching purposefully, putting everything in their mouth. Solids may start around now. Babies make a wider range of sounds, including "raspberry" blowing noises, and start to recognize their name.
Many babies sit briefly without support around 6 months, but the wobbly tripod sit (leaning on hands) is more typical at this age than independent sitting.
7 to 9 months
Independent sitting becomes solid. Babies start working on getting into and out of sitting on their own. Many start commando-crawling (army crawl) before classic crawling, and some skip crawling entirely. Babbling becomes more rhythmic, with consonant-vowel combinations like "ba-ba-ba" and "ma-ma-ma," though the sounds aren't yet attached to meaning.
Object permanence kicks in around this period, which is also why peekaboo suddenly becomes hilarious and why some babies start protesting when a parent leaves the room (the famous separation anxiety, often peaking around 8 to 10 months).
9 to 12 months
A lot happens fast in this stretch. Pulling to stand, cruising along furniture, finger feeding, waving, clapping, the pincer grasp (picking up small items with thumb and forefinger). The first real word usually arrives between 10 and 14 months. "Mama" or "Dada" used with intention to refer to the parent counts.
Most babies are not walking by 12 months. They're getting close.
12 to 15 months
The first independent steps usually happen between 11 and 15 months. Some early walkers are pulling up at 7 months and walking at 9 months. Some don't take steps until 16 or 17 months and turn out completely typical. Walking age has very little correlation with future motor skill or coordination.
Vocabulary expands slowly, often a handful of words by 15 months. Pointing to communicate (asking for something, showing you something they noticed) is a big developmental marker that often gets less attention than walking but matters more for language.
15 to 18 months
Walking gets confident. Babies start running awkwardly. Vocabulary picks up to 5 to 20 words for many toddlers, though the range is huge. Following simple one-step commands ("get your shoe") becomes consistent. Scribbling, stacking a couple of blocks, drinking from an open cup. Tantrums show up as language frustration grows ahead of language ability.
When to mention something to a pediatrician
A few specific markers that warrant a conversation, not because they mean something is wrong but because they're worth a closer look:
- No social smiling by 3 months. The first responsive smile is one of the most consistent early developmental markers.
- Not rolling either direction by 6 to 7 months. Some babies skip rolling, but most do it by this age.
- Not sitting without support by 9 months. This is the standard cutoff for a developmental check-in.
- No babbling with consonants by 12 months. "Mama" or "baba" sounds, even without meaning, should be there.
- No first word by 15 to 16 months. Many late talkers catch up fully, but it's worth flagging.
- Not walking by 18 months. A wide range is normal up to 18 months. Past that, it warrants a closer look.
Two other things that matter, separately:
A skill that was once present and disappears. A baby who used to babble and stops, or used to wave and doesn't anymore, or used to make eye contact and pulls back. Regression in skills is a more concerning pattern than late acquisition of skills, and it's worth a same-week call.
No new skills emerging across several months. A baby who has been at the same developmental place for 3 or 4 months with no new abilities is worth checking in about. Steady progress, even slow progress, is more reassuring than late starts.
A small note on tracking
Pediatricians ask milestone questions at every well-baby visit. If you've ever frozen up trying to remember when your baby first rolled or said their first word, you're not alone. You don't need to log every developmental moment, but jotting down the big firsts in a notes app or in Tottli means you have an actual answer instead of a guess.
It's also a small gift to your future self. The early months blur together, and you'll forget more than you expect.
A reframe on milestones
A baby who is steadily acquiring new skills, on whatever timeline, is generally fine. The trajectory matters more than the timing. Some babies are early at gross motor and late at language. Some are the reverse. Some hit everything right around the average and feel completely standard. Some are genuinely advanced in one area and quirky in others.
The CDC's shift to a 75th-percentile framing is helpful because it acknowledges the variation. Ten or twenty years ago, parents were told their baby "should" be doing things by ages that, in retrospect, half of all babies didn't hit. That created a huge amount of unnecessary worry.
If you take one thing away
Worry less about whether your baby is on the chart this month. Watch for the trajectory: Are they gaining new skills? Did anything they used to do disappear? Has there been a long stretch with no progress?
Steady forward motion, no matter the pace, is the answer to almost every milestone question parents have. Your job isn't to push the timeline. It's to notice the direction, give them the time and space to develop, and check in with the pediatrician about anything that doesn't fit.