WHO Windows of Achievement for Gross Motor Milestones
Should my child have a WHO-GMM assessment?
The WHO Windows of Achievement for Gross Motor Milestones (WHO-GMM) is a reference framework describing the wide, normal age ranges for six motor milestones — sitting, crawling, standing and walking — not a stand-alone test. Most children don't need a separate WHO-GMM assessment; clinicians use the windows as one lens within a fuller developmental check. It's most useful when there is a specific concern, such as a child clearly past a window or losing a skill, in which case a proper review is wise.
Curious whether your little one's rolling, sitting and walking are on track? Here's what the WHO gross-motor windows really tell you.
In short
The WHO Windows of Achievement for Gross Motor Milestones (WHO-GMM) is a reference framework — not a stand-alone test — that describes the broad age ranges in which healthy children typically reach six motor milestones: sitting without support, hands-and-knees crawling, standing with assistance, walking with assistance, standing alone, and walking alone. Most children do not need a separate "WHO-GMM assessment"; rather, a clinician uses these windows as one lens within a fuller developmental check. It is worth a look if your child seems clearly behind on gross-motor steps, but the windows are deliberately wide because healthy babies vary a great deal.What the windows actually involve
The WHO milestones come from a large multi-country study of healthy children, so each milestone is given as a window (for example, walking alone anywhere from roughly the end of the first year into the second), not a single deadline:- Six gross-motor milestones — observed through everyday movement, not a pass/fail exam.
- Wide, overlapping ranges — designed to reflect normal variation across babies and cultures.
- Observation, not equipment — a clinician watches how your child moves, holds posture, bears weight and transitions between positions.
- One piece of the picture — gross motor is read alongside fine motor, communication, social and play development.
So the honest answer to "should my child have one?" is: the windows are most useful when there is a specific concern — your child is well past a window, has lost a skill, or moves very differently on one side. In those cases the windows become a helpful prompt to seek a proper review.
When to seek a check
Book a developmental review if your child is clearly past a window (for example, not sitting with support well beyond the typical range, or not walking by around 18 months), has stiff or floppy muscle tone, strongly favours one side, or has lost a skill they once had. Persistent, marked delay deserves prompt attention — early movement support is gentle and effective.The Pinnacle way
A clinical AbilityScore® and any diagnosis are formed only at a Pinnacle Blooms Network centre, under the care of a qualified clinician — never from an online chart or a single milestone window. Our clinicians use a structured, clinician-administered assessment that places gross-motor progress within your child's whole developmental picture, measured against their own baseline so real gains become a clear line. Backed by 2.5 billion+ data points and 25 million+ therapy sessions across 70+ centres, we turn each review into practical occupational and physical movement support you can use at home. You can read how the measure works here: what the AbilityScore is and how it's calculated.Trusted sources
WHO Motor Development Study and Windows of Achievement for six gross-motor milestones; WHO and Nurturing Care guidance on early childhood development; CDC and HealthyChildren (AAP) developmental milestone resources for movement.Next step — Not sure if your child's movement is on track? Book a developmental assessment with a Pinnacle clinician for clear, reassuring answers and a plan if needed.
This is general information, not a diagnosis — a clinical AbilityScore® and any diagnosis are formed only at a Pinnacle Blooms Network centre under qualified clinician care.
What to watch
Watch whether your child reaches sitting, crawling, standing and walking within the broad WHO windows, and how smoothly they transition between positions. Seek a review if your child is clearly past a window, has stiff or floppy tone, strongly favours one side, or loses a skill they once had.
Try this at home
Give plenty of supervised floor and tummy time every day — it's where babies build the strength to roll, sit, crawl and pull to stand. Place a favourite toy just out of reach to gently invite movement, and let your child practise at their own pace.
Trusted sources
Developed by SETU Consortium · Pinnacle Blooms Network · Last reviewed 2026-06-10 · reviewed every 365 days
This is general information, not a diagnosis. A clinical AbilityScore® and any diagnosis are formed only at a Pinnacle Blooms Network centre, under qualified clinician care.
Frequently asked
Is the WHO-GMM a test my child must pass?
No. The WHO Windows of Achievement describe wide, normal age ranges for six gross-motor milestones rather than a pass/fail exam. They are observed through everyday movement and used as one lens within a fuller developmental review.
My baby isn't walking yet — should I worry?
The walking window is wide and most children walk somewhere across the late first year into the second. If your child is clearly past the typical range (for example not walking by around 18 months), has unusual muscle tone, or favours one side, book a developmental review for reassurance and a plan if needed.
Does Pinnacle use the WHO windows to diagnose my child?
No single chart or window forms a diagnosis. A clinical AbilityScore® and any diagnosis are formed only at a Pinnacle Blooms Network centre under a qualified clinician, who places gross-motor progress within your child's whole developmental picture.