Milestone Guess: When Do Babies Roll, Sit and Walk?

Name: Milestone Guess
Author: Cynthia Obinatu

Guess the age for eight baby milestones, from the first smile to the first words. After each guess you see the usual range and where it comes from. Every baby moves at their own pace.

This game needs JavaScript. Here are all the answers and their sources.

By what age do most babies smile back when you talk to them or smile at them? By 2 months. The CDC says most children (75 percent or more) smile when you talk to or smile at them by 2 months. The CDC's 2-month list also includes settling when spoken to or picked up, and looking at your face. Milestones are checkpoints, and some babies reach them earlier or later. Source: CDC: Milestones by 2 months.
By what age do most babies laugh out loud? By 6 months. The CDC lists laughing at 6 months. At 4 months, many babies chuckle when you try to make them laugh. At 4 months the CDC lists a chuckle that is not yet a full laugh. The full laugh is on the 6-month list. Source: CDC: Milestones by 4 months; CDC: Milestones by 6 months.
By what age do most babies roll from tummy to back? By 6 months. The CDC lists rolling from tummy to back at 6 months. The CDC also lists pushing up with straight arms on the tummy at 6 months. Babies reach these at their own pace. Source: CDC: Milestones by 6 months.
By what age do most babies sit without support? By 9 months. The CDC lists sitting without support at 9 months. WHO found babies sat alone anywhere between about 4 and 9 months, with the middle at about 6 months. Sitting has the narrowest window of the six motor milestones WHO studied, but it still spans about 5 months. Source: CDC: Milestones by 9 months; WHO Motor Development Study (Acta Paediatrica, 2006).
At what age do most babies start crawling on hands and knees? Around 8 months in the middle, with a wide window of about 5 to 13 months. That is the WHO range for hands-and-knees crawling. In the WHO study, about 4 in every 100 babies never crawled on hands and knees, and some babies move around another way, such as shuffling on their bottom. That is inside the range. The CDC does not list crawling as a milestone. Source: WHO: Windows of achievement for six gross motor milestones; WHO Motor Development Study (Acta Paediatrica, 2006).
By what age do most babies call a parent "mama", "dada" or another special name? By 12 months. The CDC lists calling a parent "mama", "dada" or another special name at 1 year. At 9 months the CDC lists making many different sounds, like "mamamama" and "bababababa". The special name comes a few months later. Source: CDC: Milestones by 9 months; CDC: Milestones by 1 year.
At what age do most babies walk on their own? Around 12 months in the middle, with a window of about 8 to 17 months. That is the WHO range for walking alone. The CDC lists a few steps alone at 15 months and walking without holding on at 18 months. A baby who walks at 16 months is inside the range, and so is one who walks at 9 months. Source: WHO: Windows of achievement for six gross motor milestones; WHO Motor Development Study (Acta Paediatrica, 2006); CDC: Milestones by 18 months.
By what age do most children try to say three or more words besides "mama" and "dada"? By 18 months. The CDC lists trying to say three or more words besides "mama" or "dada" at 18 months. At 15 months the CDC mark is one or two words besides "mama" or "dada". If you worry about your child's words, ask at a check-up. Source: CDC: Milestones by 18 months.

Your guesses, with the ranges

Educational, not medical advice. Milestone ages are usual ranges, and they cannot tell you anything about your own baby. Babies develop at very different rates, and reaching something later is often completely normal. The game runs on your phone. Nothing you pick is saved or sent anywhere.

When to speak to a doctor

Mention it at a check-up if your baby is not meeting several milestones for their age, seems to lose a skill they had, does not respond to sounds or faces, or if your instinct says something is different. Early support helps, and asking is never an overreaction. A late milestone is not a failure, and a score in this game says nothing about your baby.

Written by Cynthia Obinatu, community and editorial lead. Sourced, not yet reviewed by a clinician.

How Milestone Guess works

You will see eight milestones that many parents watch for. Guess the age by tapping one of four choices. You score 2 points for the usual age, 1 point for a near guess and 0 for a guess far off. The usual age and its source show straight away.

Read one milestone at a time.
Tap the age you think is usual.
Read the range and open the source.
See your score and send it to a friend.

Where the ages come from

The "by" ages come from the CDC's "Learn the Signs. Act Early." milestone lists, which show what most children (75 percent or more) can do by that age. The movement ages for sitting, crawling and walking come from the WHO Motor Development Study, which followed children from Ghana, India, Norway, Oman and the USA, and shows a wide window for each milestone. These are the same sources as the Baby Milestone Tracker.

A range is not a deadline. The CDC says a milestone is something most children can do by an age, so some children reach it earlier and some later. Use the game to learn the ranges, and use your clinic visits to talk about your own baby.

To see what many babies do at each age, open the Baby Milestone Tracker. For first foods after 6 months, read Starting solids.

Common questions

Is a late milestone a problem?

Not by itself. Babies develop at very different rates, and the ranges are wide. Mention it at a check-up if your baby is not meeting several milestones, loses a skill, or you feel something is different.

Why are some ages a range and others a "by" age?

The CDC lists the age by which most children have reached a milestone. WHO gives a window from the earliest to the latest ages in a healthy group of children. The page says which one each answer uses.

My baby never crawled. Is that a worry?

In the WHO study, about 4 in every 100 babies never crawled on hands and knees. Some babies move around another way. Mention it at a check-up if you want to ask.

Is my score saved?

No. Your picks stay on your phone. If you share your result, the link and the picture show your result only, never your picks.

Where this comes from

CDC: Milestones by 2 months. US Centers for Disease Control and Prevention.
CDC: Milestones by 4 months. US Centers for Disease Control and Prevention.
CDC: Milestones by 6 months. US Centers for Disease Control and Prevention.
CDC: Milestones by 9 months. US Centers for Disease Control and Prevention.
WHO Motor Development Study (Acta Paediatrica, 2006). World Health Organization.
WHO: Windows of achievement for six gross motor milestones. World Health Organization.
CDC: Milestones by 1 year. US Centers for Disease Control and Prevention.
CDC: Milestones by 18 months. US Centers for Disease Control and Prevention.

Every answer is checked against the sources above and is not yet reviewed by a clinician. Read it alongside our editorial policy and medical policy.

Go further

The First Baby Playbook

A community for parents in the baby and toddler years, guidance on sleep, feeding and milestones, and a professional to ask.

See the program →

Milestone Guess: When Do Babies Roll, Sit and Walk?

When to speak to a doctor

How Milestone Guess works

Where the ages come from

Common questions

Where this comes from

The First Baby Playbook

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Baby Milestone Tracker

Paediatric Visit Questions

Starting solids: first foods