Enter your baby's due date to see when each of the 10 mental leaps is expected, which leap or calm "sunny" period your baby is in today, and a visual chart of the fussy weeks for the first 20 months.
Last updated:
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Age from due date–
Age from birth–
Next leap starts–
Fussy-period chart
All 10 leaps
Leap
Fussy weeks
Dates
New skills to watch for
Status
Leap weeks are averages from a popular parenting theory. Every baby is different; this is not medical advice.
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How to use the Baby Leaps Calculator
Enter the due date. Leap timing is counted from the due date, not the birth date, because it follows brain development since conception.
Optionally add the birth date to see how early or late your baby arrived and the age from birth.
Press Calculate leaps to see today's leap status and the full list of leap dates.
Read the chart: shaded bars are the fussy periods, and the line marks the date you are checking.
Save the dates with Add to calendar (.ics) or Copy dates.
Leap chart: weeks and approximate ages
Leap
Fussy weeks (from due date)
Approximate age
Theme
1
4.5–5.5
About 1 month
Sensations
2
7.5–9.5
About 2 months
Patterns
3
11.5–12.5
About 3 months
Smooth transitions
4
14.5–19.5
About 4 months (often the longest)
Events
5
22.5–26.5
About 6 months
Relationships
6
33.5–37.5
About 8 months
Categories
7
41.5–46.5
About 10 months
Sequences
8
50.5–54.5
About 12 months
Programs
9
59.5–64.5
About 14 months
Principles
10
70.5–75.5
About 17 months
Systems
Each leap's date is the due date plus the number of weeks shown (for example, 4.5 weeks = 32 days after the due date). A baby born 3 weeks early will usually reach leap 1 about 7.5 weeks after birth.
Signs a leap may be starting
More crying, clinginess and wanting to be held
Shorter naps or more night waking
Changes in appetite, such as wanting to feed more often for comfort
Shyness with other people and protest when a parent leaves
After a few days to weeks: a burst of new skills and a calmer mood
Tips for getting through a fussy period
Offer extra closeness: babywearing, cuddles and skin-to-skin time help many babies settle.
Keep routines simple and lower expectations for outings and visitors during the predicted weeks.
Play with the new skill: once your baby shows something new, give them chances to practise it.
Look after yourself: share night duties where possible and remember that the phase passes.
Rule out other causes: fever, poor feeding or unusual sleepiness are not signs of a leap; call your pediatrician.
Frequently asked questions
What are baby leaps?
Baby leaps are short periods when an infant suddenly becomes fussier, clingier and cries more, often followed by a new set of skills. The idea comes from the popular leap theory developed by researchers Hetty van de Rijt and Frans Plooij, who described 10 predictable leaps in the first 20 months. It is a helpful framework for many parents, not a medical standard.
Why are leaps calculated from the due date?
The theory links leaps to brain maturation since conception, so a baby born two weeks early is expected to reach each leap about two weeks later after birth than a baby born on the due date. Using the due date keeps the timing the same for premature and late babies.
When are the 10 leaps?
Commonly cited fussy periods are around week 4.5–5.5 (leap 1), 7.5–9.5 (leap 2), 11.5–12.5 (leap 3), 14.5–19.5 (leap 4), 22.5–26.5 (leap 5), 33.5–37.5 (leap 6), 41.5–46.5 (leap 7), 50.5–54.5 (leap 8), 59.5–64.5 (leap 9) and 70.5–75.5 (leap 10), counted in weeks after the due date.
Is every baby fussy at exactly these times?
No. The weeks are averages and many babies start a leap a week early or late, show only mild signs, or are fussy for other reasons such as illness, teething or growth spurts. Use the dates as a rough guide and follow your baby's cues.
What is a sunny period?
It is the calmer stretch between leaps, when a baby has absorbed the new skills and is usually happier and easier to settle. The calculator shows sunny periods as the gaps between the shaded fussy weeks.
When should I call a doctor instead of blaming a leap?
Contact your pediatrician if your baby has a fever, is feeding poorly, has fewer wet diapers, is unusually sleepy or hard to wake, cries inconsolably for hours, or if you are worried. Leaps never cause illness symptoms, and this tool does not give medical advice.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.