Growth spurt windows & signs

Baby Growth Spurt Calculator

Q: When do baby growth spurts happen?

Baby growth spurts typically occur at predictable ages: around 3 weeks, 6 weeks, 3 months, 6 months, and 9 months. Additional spurts can happen around 12, 18, and 24 months. Not every baby shows obvious signs at every window.

Q: How long does a baby growth spurt last?

Most growth spurts last 2–7 days, though some stretch to about 2 weeks. Expect increased hunger, disrupted sleep, and extra fussiness during this window, returning to normal once the spurt ends.

Q: How do I know if my baby is having a growth spurt?

Common signs include sudden increased hunger or cluster feeding, more fussiness or crying, changes in sleep (more or less than usual), and needing extra comfort. These typically cluster around the known spurt windows.

Q: Does a baby sleep more during a growth spurt?

Many babies do, since growth hormone is largely released during sleep. Some babies instead wake more often due to hunger. Both patterns are normal.

See typical growth spurt windows by age, plus calculate your baby's exact weight and height percentile.

Growth spurt timeline

3 weeks old

Duration: 1–3 days

Frequent feedingFussinessMore sleep

6 weeks old

Duration: 2–3 days

Cluster feedingClingy behaviorShorter naps

3 months old

Duration: 3–5 days

Increased appetiteSleep regressionDrooling

6 months old

Duration: 3–5 days

Appetite surgeNight wakingMotor milestone prep

9 months old

Duration: 3–5 days

Food interest peaksCrawling/pulling upSeparation anxiety

12 months old

Duration: 4–7 days

Walking prepAppetite may dipVocabulary surge

18 months old

Duration: 5–7 days

Language leapSleep disturbancesClingy & emotional

2 years old

Duration: 1 week

Appetite fluctuationsAssertivenessFine motor advances

WHO · CDC · IAP · UK-WHO Standards

Infant Growth Percentile Calculator.

Enter your baby's measurements and location to see percentiles on the most appropriate growth chart for your region — with interactive curves, growth spurt indicators, and a printable report.

Age — years

Age — months

Gender *

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Country / Region (optional)

Race / Ethnicity (optional)

Reference standard

WHO is recommended for infants under 2 years globally. CDC is used by US pediatricians. Select a country above to auto-fill the best standard.

Weight

Height / Length

Premature birth (corrected age)

If born before 37 weeks, corrected age adjusts all percentiles until 24–36 months.

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Multi-child dashboard.

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Calculate your baby's percentiles above, then click "Save to Dashboard" to track growth over time.

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Frequently asked questions

When do baby growth spurts happen?

How long does a baby growth spurt last?

How do I know if my baby is having a growth spurt?

Does a baby sleep more during a growth spurt?

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Baby Growth Spurt Calculator

Growth spurt timeline

Infant Growth Percentile Calculator.

Weight-for-age

Height-for-age

What do these numbers mean?

Multi-child dashboard.

Frequently asked questions