In the first year, babies change almost weekly. What starts as uncoordinated kicking turns into grasping, sitting, babbling, crawling, first steps — sometimes in just a few days. This guide shows what developmental milestones most babies reach at each age.
We follow the CDC's revised 2022 framework ("Learn the Signs. Act Early.") and AAP Bright Futures recommendations — the most rigorously validated milestone list in clinical use today.
The eight reference ages
The CDC defines eight checkpoint ages where typical developmental skills can be observed: 2, 4, 6, 9, 12, 15, 18 and 24 months. These align with well-child visits in most countries.
For each age, four domains are evaluated: Motor (gross and fine motor), Language (sounds, comprehension), Social/Emotional (relationships, play), and Cognitive (learning, problem-solving).
Quick overview — what's typical when
| Age | Typical milestone |
|---|---|
| 2 months | Smiles socially, briefly lifts head when on tummy |
| 4 months | Babbles, holds head steady, reaches for toys |
| 6 months | Rolls both ways, transfers objects between hands |
| 9 months | Sits without support, beginning pincer grasp, stranger anxiety |
| 12 months | Pulls up to stand, says 'mama'/'dada' specifically, waves |
| 15 months | Walks, scribbles, points with finger, follows simple commands |
| 18 months | Says 6–10 words, eats with spoon, basic pretend play |
| 24 months | 2-word phrases, runs steadily, kicks a ball, sorts by shape |
This table is a selection. The full list with watch-out signs is built into the interactive Baby Milestones Calculator.
The four domains explained
- Motor — gross motor (sitting, rolling, standing, walking) and fine motor (grasping, pincer grasp, drawing). Often the most visible domain and usually noticed first by parents.
- Language — from cooing to babbling, first words, two-word phrases. Receptive (understanding) develops well before expressive (speaking).
- Social/Emotional — social smile, stranger anxiety, favorite people, temper tantrums. Easy to overlook but central to attachment.
- Cognitive — attention, object permanence, problem-solving, symbolic understanding. Hard to measure directly, but typical play sequences give good clues.
When to call the pediatrician
The CDC lists specific watch-out signs ("Act Early signs") for every checkpoint. The strongest cross-cutting indicator is a loss of skills already gained. If your baby said "mama" at 9 months and stopped by 12 months — that's always a reason to ask.
Other classic concerns: no reaction to loud sounds (2 mo), no smiling (4 mo), can't sit with help (6 mo), can't bear weight on legs (9 mo), no pointing to show interest (15 mo), no two-word phrases (24 mo).
Premature babies — corrected age
For premature babies (born before 37 weeks of gestation), use the corrected age. Example: born at 35 weeks (5 weeks early), actual age 12 months → corrected age ~11 months. The AAP recommends correction up to age 2. After that, most children catch up.
Growth: not just milestones matter
Beyond milestones, physical growth is also a key indicator. Weight, length and head circumference are plotted on WHO growth curves at every visit. A consistent percentile (e.g. P50) matters more than the absolute number.
To understand growth curves, percentiles and z-scores in depth, see our child growth percentile guide.
Related calculators
- Child growth percentile — track weight, length, head circumference. See the growth percentile guide.
- APGAR score — the first newborn vitality check. See the APGAR guide.
- Due date — basis for age correction in premature babies. See the due date calculator.
Check your baby's milestones now
Pick an age or enter a birth date — get an instant overview of what's typical right now.
Open Baby Milestones Calculator →Frequently asked questions
Which milestones matter most in the first year?
Social contact (smiling, eye contact), language (babbling, first words) and gross motor (sitting, crawling, standing). Since 2022, the CDC has emphasized social and language skills as the most reliable early indicators.
My child is slower than peers — should I worry?
A single delayed milestone in an otherwise alert, social child is usually normal. If multiple domains lag at once or your child loses skills, see the pediatrician.
How can I support development?
Talk to your baby, read aloud, allow plenty of floor time, create safe spaces to explore, avoid screen time under 2 (AAP recommendation). The biggest factor is attentive bonding.
Are routine well-child visits enough?
Yes. Visits at 2, 4, 6, 9, 12, 15, 18 and 24 months align directly with the CDC framework and are covered by most insurance. Between visits, occasional informal tracking is plenty — and you can always book a midpoint visit if something concerns you.