Baby leap calculator: dates of all 10 leaps by week

Which leap window is your baby in now? Enter the birth date, plus the due date if born early, for the 10 leap windows from week 5 to week 75.

How to use the leap calculator

  1. Enter your baby's birth date. If your baby was born early, add the due date too: the calculator counts the leaps from the due date when your baby came 3 to 17 weeks early (see "Born early?" below).
  2. Read the timeline. You get 10 leap windows, from about week 5 to week 75. Each shows a start and end date and whether it has passed, is happening now or is still coming up.
  3. Tap a leap on the timeline to see what tends to change for babies in that period.

The calculator answers one question: when are the leap windows for your baby? For what a developmental leap is and the signs parents describe, read our developmental leaps guide.

The 10 leap windows at a glance

LeapWindow starts aroundWhat tends to change
1Week 5Wide awake and alert: more awake, taking in more light, sound and touch
2Week 8Finding hands and voice: discovering hands, watching faces, cooing
3Week 12Moving with more control: steadier reaching and head control
4Week 19Grab, shake, repeat: trying things again and again to see what happens
5Week 26Keeping you in sight: noticing and protesting when you move away
6Week 37Taking a closer look: studying things, comparing them, pointing
7Week 46Copying what you do: imitating everyday actions
8Week 55Doing it their way: wanting more independence alongside routine
9Week 64Testing the limits: seeing how you respond
10Week 75Working things out: fitting pieces together, pretending, solving little problems

The weeks count from the birth date, or from the due date for a baby born 3 to 17 weeks early. A window is a rough guide to when a change might show, not a date on which it will.

Born early? Add the due date

The ages in the original leap research were counted from the due date rather than the birth date, so a baby born three weeks early would be expected to reach each window about three weeks later by the calendar. Pediatricians use the same idea for development in general: the American Academy of Pediatrics recommends using a premature baby's corrected age (age from birth minus the weeks born early) when you look at developmental skills during the first two years.

The calculator follows the same rules as the Nurtura Daily app: it uses the due date when your baby came 3 to 17 weeks early. Born less than 3 weeks early, or after the due date, it counts from the birth date. A due date more than 17 weeks after the birth date is most likely a typing mistake, so it isn't used.

How this is calculated

The calculator adds a fixed number of weeks (5, 8, 12, 19, 26, 37, 46, 55, 64 and 75 weeks) to the birth date, plus the weeks born early when the due date is used, and shows a 10-day window starting on each one. That is all it does: it does not use your baby's weight, feeding or sleep, and it cannot tell whether your baby is in a leap right now.

The ages follow the "regression periods" described by Hetty van de Rijt-Plooij and Frans Plooij, who followed a small group of babies and their mothers at home and reported short periods of extra crying, clinginess and unsettled behavior at similar ages, each followed by new skills. A later study in Catalonia using the same method also found these periods in the first year. The studies were small, and babies differ, so treat the windows as approximate. Not every baby shows every leap, and not every fussy week is a leap.

When fussiness is not a leap

Most unsettled days have everyday causes: hunger, tiredness, gas, a wet diaper, being too hot or cold, or simply wanting a cuddle. The NHS advises contacting your GP or NHS 111 (or your local doctor) if your baby cries constantly and can't be settled, the cry doesn't sound like their usual cry, or they show signs of being unwell, such as a high temperature or not being interested in feeding. Call emergency services straight away for signs like difficulty breathing, a fit, blue or gray skin, or a rash that doesn't fade when pressed. Don't put off getting help because a leap window is on the calendar.

Track what actually changes

Leap windows are most useful next to what really happens. Logging sleep, feeds and new skills in Nurtura Daily lets you look back at a rough week and see whether it lined up with a leap window or had another cause, and, with Pro, the app can remind you when the next window is coming up.

Sources

Written by the Nurtura Daily team. This calculator is general information, not medical advice.

What is a baby leap calculator?

It estimates when your baby's developmental leap windows fall. Enter a birth date (and a due date if your baby was born early) and it lists 10 approximate windows, from about week 5 to week 75, with what tends to change in each.

What leap is my baby in right now?

Enter your baby's date above: a leap whose window includes today is marked **Happening now**, and the next one shows how far away it is. The windows are approximate, so your baby's behavior is a better guide than the calendar.

Should I use the birth date or the due date?

Enter the birth date, and add the **due date** if your baby was born early. When your baby came 3 to 17 weeks early, the calculator counts from the due date: the ages in the original research were counted from it, just as doctors use corrected age for premature babies' development. Born less than 3 weeks early, or late, it uses the birth date.

How accurate are the leap dates?

They are rough windows, not predictions. The timing comes from small observational studies, and babies vary. Some babies show a clear change around a window, some show it earlier or later, and some barely seem to notice.

Do all babies go through the same leaps?

Not in the same way. Researchers described similar periods across the babies they studied, but the timing and how noticeable each one is differ from baby to baby. Not every fussy week is a leap.

Can a leap affect sleep and feeding?

Parents often report more night waking, shorter naps or changes in feeding around these periods. If your baby isn't interested in feeding, has fewer wet diapers than usual, or seems unwell, contact your doctor or health visitor rather than waiting for a leap to pass.

How can I help my baby through a leap?

Extra closeness usually helps: holding, feeding on cue, a calm environment and a bit more patience with routines. The same everyday soothing that works for any unsettled day works here too.

Is the leap schedule scientifically proven?

It is based on published observational research by Hetty van de Rijt-Plooij and Frans Plooij, and a study in Catalonia found similar periods. The studies were small, so the schedule is a helpful framework rather than an established medical fact. It isn't a diagnosis or a developmental test.