# What is the WHO Windows of Achievement for Gross Motor Milestones (WHO-GMM)?

Canonical: https://pinnacleblooms.org/ask/what-is-the-who-windows-of-achievement-for-gross-motor-milestones-who-gmm-and-what-does-it-assess
Publisher: Pinnacle Blooms Network / Bharath Healthcare Laboratories Private Limited

The WHO Windows of Achievement for Gross Motor Milestones (WHO-GMM) is a World Health Organization reference describing the typical age ranges in which healthy children worldwide reach six big-movement milestones: sitting without support, standing with assistance, hands-and-knees crawling, walking with assistance, standing alone and walking alone. It assesses when, not how well, these skills appear by giving a normal window of months for each rather than a fixed deadline, reflecting healthy variation. It is a population reference for understanding typical development, not a diagnostic test for an individual child.

*Six simple movement milestones, and the natural age ranges in which healthy children around the world reach them — that is the WHO Windows of Achievement.*

## In short
The **WHO Windows of Achievement for Gross Motor Milestones (WHO-GMM)** is a research-based reference, published by the World Health Organization, that describes the typical age ranges in which healthy children reach six key gross-motor (big-movement) milestones. It assesses *when* — not *how well* — a child sits, stands and walks, by giving a normal *window* of months for each skill rather than a single fixed deadline. It is a guide for understanding healthy variation, not a diagnostic test.

## What the WHO-GMM looks at
The WHO-GMM grew from a large multi-country study that followed healthy, well-nourished children across diverse settings, confirming that early motor development follows a remarkably similar pattern worldwide. It maps six milestones, each with its own age *window*:

- **Sitting without support**
- **Standing with assistance**
- **Hands-and-knees crawling**
- **Walking with assistance**
- **Standing alone**
- **Walking alone**

The gift of the *window* idea is reassurance: there is no single "right" month to walk or sit. Each milestone has a broad, healthy range, so a child who walks at 11 months and one who walks at 15 months can both be developing perfectly typically. The WHO-GMM also gently notes that not every child crawls in the classic way — some bottom-shuffle or move differently — and still reach walking well. It is a population reference for typical development, used to understand patterns, not to label an individual child.

## When to seek a review
Windows are wide, but they do have outer edges. Consider a developmental review if your child has clearly passed the upper end of a window without showing the skill — for example, not sitting independently or not walking by the ages your paediatrician flags — or if you notice your child losing a skill they once had, very stiff or very floppy movement, or strong one-sided preference in the early months. These are reasons to check in early, calmly, so that any helpful support can begin while development is most responsive.

## The Pinnacle way
This is general information, not a diagnosis — a clinical [AbilityScore®](/ask/what-is-the-abilityscore-and-how-is-it-calculated) and any diagnosis are formed only at a Pinnacle Blooms Network centre, under qualified clinician care, never from an app or form. Our clinicians use references like the [WHO-GMM](/who-gmm) alongside structured assessment of your child's whole movement picture, and where helpful build an individualised plan that may draw on [occupational therapy](https://www.pinnacleblooms.org/best-occupational-therapy-center-india-proven-improvement-rate) and other supports.

## Trusted sources
WHO Multicentre Growth Reference Study on motor development milestones and their age windows; WHO Nurturing Care Framework on early childhood development; CDC and HealthyChildren guidance on gross-motor milestones and healthy variation.

**Next step —** If you want to understand where your child sits within the WHO motor windows, book a gentle developmental review to map their movement strengths and start any helpful support early.

## Sources
- WHO Child Growth Standards & motor development milestones: https://www.who.int/tools/child-growth-standards
- WHO Nurturing Care Framework for early childhood development: https://nurturing-care.org
- CDC developmental milestones guidance: https://www.cdc.gov/child-development

## Connected topics and perspectives
- Assessments: https://pinnacleblooms.org/ask/assessments
- Parent: https://pinnacleblooms.org/ask/lens/stakeholder/parent
- Definition: https://pinnacleblooms.org/ask/lens/intent/definition
- Measure: https://pinnacleblooms.org/ask/lens/lifecycle/measure
- Screen: https://pinnacleblooms.org/ask/lens/route/screen
- Early Clarity: https://pinnacleblooms.org/ask/lens/empowerment/early_clarity

## Related question paths

### Understand the subject
- At What Age Is the WHO-GMM Used for a Child?: https://pinnacleblooms.org/ask/at-what-age-is-the-who-gmm-developmental-assessment-used-for-a-child

### Recognise signs & concerns
- Key motor milestones in early childhood: https://pinnacleblooms.org/ask/what-are-the-key-motor-milestones-in-early-childhood

### Understand assessment
- Should My Child Have a WHO-GMM Assessment?: https://pinnacleblooms.org/ask/should-my-child-have-a-who-gmm-assessment-and-what-does-it-involve
- When is the WHO-GMM indicated, and what are its strengths and limits?: https://pinnacleblooms.org/ask/when-is-the-who-gmm-indicated-and-what-are-its-strengths-and-limits-in-early-childhood
- How does the WHO-GMM compare with the AbilityScore developmental assessment?: https://pinnacleblooms.org/ask/how-does-the-who-gmm-compare-with-the-abilityscore-developmental-assessment

### Explore therapy & support
- How do I check if my child's motor development is on track?: https://pinnacleblooms.org/ask/how-do-i-check-if-my-child-s-motor-development-is-on-track