- The WHO Motor Development Study covers six milestones, each with its own window of achievement and median age
- Sitting without support: 3.8–9.2 months · Median 5.9
- Standing with assistance: 4.8–11.4 months · Median 7.6
- Hands-and-knees crawling: 5.2–13.5 months · Median 8.5
- Walking with assistance: 5.9–13.7 months · Median 9.2
- Standing alone: 6.9–16.9 months · Median 11.0
- Walking alone: 8.2–17.6 months · Median 12.1
- Tummy time and supervised floor time are the best preparation for all six
The WHO Motor Development Study — Where the Numbers Come From
The World Health Organization's Motor Development Study, part of the same 2006 research programme behind the WHO Child Growth Standards, followed a large, healthy, international sample of children and recorded the age at which each one achieved six specific gross motor milestones. From that data, WHO published a "window of achievement" for each milestone — the age range within which most healthy children reach it — along with a median age, the point by which half of children have achieved it.
This is a genuinely useful standard because it's based on direct observation of healthy children's actual development, not a theoretical timetable. The windows are intentionally wide, because gross motor development depends on strength, balance, and coordination that mature at individual rates.
The Six WHO Milestones, In Full
| Milestone | WHO Window of Achievement | Median |
|---|---|---|
| Sitting without support | 3.8–9.2 months | 5.9 months |
| Standing with assistance | 4.8–11.4 months | 7.6 months |
| Hands-and-knees crawling | 5.2–13.5 months | 8.5 months |
| Walking with assistance | 5.9–13.7 months | 9.2 months |
| Standing alone | 6.9–16.9 months | 11.0 months |
| Walking alone | 8.2–17.6 months | 12.1 months |
Sitting independently, without hands for balance, is usually the first of the six milestones. For the full breakdown of stages leading up to it, see our guide to when babies sit up.
Pulling up to a standing position using furniture, a caregiver's hands, or anything within reach — a significant moment where a baby bears full weight on their legs for the first time. This often overlaps with crawling readiness in the timeline.
Often called "cruising" — moving sideways along furniture in a standing position, supported by the hands. This builds the weight-shifting and balance that independent walking requires.
Balancing upright without any support, even briefly — a direct precursor to independent walking, and often achieved within weeks of the first unsupported steps.
The final milestone in the WHO study, and usually a gradual build of confidence rather than a single leap. For the full picture, see our guide to when babies start walking.
How to Support Gross Motor Development
Daily tummy time
Builds the neck, back, shoulder, and core strength every one of the six milestones depends on.
Generous supervised floor time
Time on a firm, flat surface gives your baby space to practise movement — far more effective than time in seats or bouncers.
Toys placed just out of reach
Motivates reaching, rolling, and eventually crawling or pulling up to get to something interesting.
Stable furniture for pulling up
Low, sturdy furniture gives a baby something safe to practise pulling up and cruising along.
Log all six milestones. See the whole developmental picture.
Track every WHO gross motor milestone with the date you first observed it, alongside the official windows for context. Free with the Lunara parenting app.
Common Gross Motor Concerns — Explained Plainly
🚀 "My baby skipped crawling entirely"
What it means: The WHO Motor Development Study itself notes that not every child follows the same order through all six milestones — a meaningful share of healthy babies, especially bottom-shufflers, skip hands-and-knees crawling entirely.
What actually matters- Whether a baby is progressing through mobility overall — pulling up, cruising, walking
- Not the specific style or sequence used to get there
⚖️ "One side seems stronger than the other"
What it means: A brief preference while learning a new skill is common, but a strong, persistent asymmetry over several weeks — one arm or leg doing significantly less work — is worth mentioning at a checkup.
What actually helps- Note how long the asymmetry has been present
- Raise it at your next well-child visit for a professional assessment
Signs of Typical Progress — and Signs Worth a Closer Look
- Steady progress through strength and coordination over months
- Shows interest in movement — reaching, rolling, scooting, pulling up
- Uses both sides of the body fairly evenly
- Milestones falling within the WHO windows of achievement, whatever the exact age
- No independent sitting by around 9 months
- No attempt at any independent movement by 12 months
- Not walking independently by 18 months
- A strong, persistent preference for one side of the body
Recording Gross Motor Milestones — Why It Helps
At well-child visits, pediatricians often ask about the sequence of gross motor milestones — when did your baby first sit, stand, crawl, or walk? Having these dates logged, rather than estimating from memory, gives your provider a clearer, more accurate picture.
Lunara's milestone tracker lets you log all six WHO gross motor milestones with the date first observed, alongside the official WHO windows for context, so you always know where your baby's progress sits.
For a broader overview across all developmental domains, see our guide to what milestones your baby should hit.
When to Speak With Your Pediatrician
Most variation within the WHO windows is completely normal. A few patterns are worth raising at or before your next scheduled visit.
🩺 Contact Your Pediatrician if You Notice:
These are worth raising, not emergencies to panic over:
Gross motor concerns:- No independent sitting by around 9 months — the upper end of the WHO window
- Not standing with support by around 12 months
- No attempt at any independent movement by 12 months
- Not walking independently by 18 months
- A strong, persistent preference for one side of the body
- A loss of a previously reached gross motor skill — always worth prompt review
Developmental timelines are general guidelines, and every baby develops at their own pace. Most babies who seem "late" on one milestone are simply at the later end of a wide, officially recognised normal range — but professional reassurance is always available if you'd like it.
Frequently Asked Questions — Gross Motor Milestones
Gross motor milestones are the large-muscle movement skills babies develop — sitting, standing, crawling, and walking — as opposed to fine motor skills, which involve smaller movements like grasping objects. The World Health Organization's Motor Development Study is the official reference for six of these gross motor milestones.
The WHO Motor Development Study, part of the same 2006 research programme behind the WHO Child Growth Standards, tracked six gross motor milestones across a large, healthy, international sample of children and published an official statistical "window of achievement" for each — the age range within which most healthy children reach that milestone.
The six milestones tracked by the WHO Motor Development Study are: sitting without support, standing with assistance, hands-and-knees crawling, walking with assistance, standing alone, and walking alone. Each has its own published window of achievement and median age.
The WHO window of achievement for standing with assistance (pulling up to stand while holding furniture or a caregiver's hands) is 4.8 to 11.4 months, with a median age of 7.6 months.
The WHO window of achievement for standing alone, without any support, is 6.9 to 16.9 months, with a median age of 11.0 months.
The six WHO windows overlap considerably because gross motor development isn't a strict sequence — a baby who's a little later to sit might still be right on schedule for standing with assistance, since each skill depends on individually developing strength, balance, and coordination rather than a fixed timetable.
Not exactly in a fixed sequence — while sitting typically comes before standing and crawling, and crawling typically before walking, a meaningful number of healthy babies skip hands-and-knees crawling entirely and move from sitting straight to pulling up, cruising, and walking. The WHO Motor Development Study itself notes that not all children follow every stage in the same order.
Skipping hands-and-knees crawling in particular is common and not a developmental concern — many babies, especially bottom-shufflers, move directly from sitting to pulling up and walking. What matters more is whether a baby is progressing through mobility overall, not whether every individual milestone is achieved in a specific style.
Daily tummy time from birth, generous supervised floor time on a firm surface, and opportunities to reach, roll, sit, and pull up in a safe space are the most effective ways to support gross motor development. Devices like walkers and bouncers are not recommended, since they support body weight rather than requiring a baby to build their own strength.
Yes — motor, cognitive, language, and social-emotional development are tracked as separate domains precisely because a child can progress at a different pace in each. A baby who's an early walker isn't necessarily an early talker, and vice versa; this is entirely normal.
For babies born before 37 weeks, pediatricians typically use adjusted (corrected) age — chronological age minus the number of weeks born early — when assessing gross motor milestones against the WHO windows, usually until around 2 years of age, since premature babies often need this extra time to catch up.
Gross motor milestones involve large muscle groups and whole-body movement — sitting, crawling, standing, walking. Fine motor milestones involve smaller, more precise movements — grasping a toy, transferring objects between hands, using a pincer grip to pick up small items. Both are tracked separately in developmental surveillance.
No — baby walkers are not recommended by the NHS or AAP, since they support a baby's weight in a way that reduces the floor-time muscle development that crawling and walking require, and they carry safety risks. Bouncers and swings used briefly aren't harmful, but extended time in any supportive seat reduces the floor time that builds gross motor strength.
Worth raising with a pediatrician: no independent sitting by around 9 months, no attempt at any independent movement by 12 months, not standing with support by around 12 months, not walking independently by 18 months, or a strong, persistent preference for one side of the body. Most delays within the WHO windows are not a concern, but a professional check is always the right call.
The Bottom Line on Gross Motor Milestones
The WHO Motor Development Study gives parents something rare in the world of developmental milestones — real, precise statistical windows built from healthy children's actual development. The wide ranges reflect genuine variation, not imprecision, and the overlapping windows mean a baby can be a little later on one milestone and right on track for the next.
What matters most across all six milestones is steady progress, not a specific age or sequence. If you're ever unsure whether your baby's progress is on track, your pediatrician can give you a far more specific answer than any general guide, including this one.
Supporting Your Baby's Gross Motor Development — Checklist
- Daily tummy time from birth
- Generous, supervised floor time on a firm surface
- Limit time in seats, bouncers, and walkers
- Stable, low furniture available for pulling up
- Log the date of each of the six milestones as it happens
- Use adjusted age if your baby was born prematurely
- Bring your log to every well-child visit
- No independent sitting by 9 months → mention to pediatrician
- No independent movement of any kind by 12 months → raise soon
- Strong persistent asymmetry → mention at checkup
- Not walking by 18 months → discuss with pediatrician
Log all six. See the whole picture.
Track every gross motor milestone — sitting, standing, crawling, walking — with the date you first observed it. Bring an accurate, complete record to every well-baby check. Alongside sleep, feeding, and growth in one profile. Free to start.