What leap is my baby in?
Enter your baby’s estimated due date and the date you want to check. The result shows the most recent approximate leap start, its name, and the next leap. For example, at 33 weeks after the due date, the result is Estimated leap 6: Categories.
A baby leap describes a theme of new discoveries in the familiar ten-stage leap chart, from Sensations to Systems. If you searched for a mental leap calculator, this is the same kind of due-date-based tool.
How to use the calculator
- Enter the estimated due date. Leave the birth date out of this calculation.
- Keep today’s date or choose another date to explore.
- Read the estimated leap and open any stage in the timeline to learn about its theme.
- Add an optional first name beside the keepsake preview, then select Print your keepsake.
The print dialog lets you print a portrait A4 or US Letter page or choose Save as PDF. The little memory lines are yours to fill in by hand. Names and dates stay in the page’s browser memory and are not saved to an account or sent to a server.
Why use the due date?
The conventional chart counts from the estimated due date, even when a baby is born earlier or later. Enter the original estimated due date directly; there is no extra adjustment to make in this tool. If you do not know it, check your pregnancy records or ask your care team instead of guessing.
For a baby born four weeks early, 12 weeks since birth is eight weeks after the due date. The American Academy of Pediatrics describes this subtraction as corrected or adjusted age when considering a premature baby’s development. That clinical use of corrected age is separate from the leap chart’s week markers.
The ten baby leaps
These are approximate starts, counted in completed weeks after the due date. The interactive timeline above turns each week into a calendar date for your baby.
| Leap | Stage | Approximate start |
|---|---|---|
| 1 | Sensations | Week 4 |
| 2 | Patterns | Week 7 |
| 3 | Smooth transitions | Week 11 |
| 4 | Events | Week 14 |
| 5 | Relationships | Week 22 |
| 6 | Categories | Week 33 |
| 7 | Sequences | Week 41 |
| 8 | Programs | Week 51 |
| 9 | Principles | Week 59 |
| 10 | Systems | Week 70 |
Worked example: a 12-week due-date age
With a due date of January 1, 2026, checking March 26, 2026 gives 84 days, or exactly 12 weeks, after the due date. The most recent start is week 11, so the result is Estimated leap 3: Smooth transitions. Its approximate start is March 19, 2026. Next is leap 4: Events, around April 9, 2026, at week 14.
The calculation is simply due date plus the stage’s week number multiplied by seven days. It does not assign an exact end date. Before week 4, the result says before leap 1; after 20 calendar months, it says beyond the chart. The complete keepsake remains available in either case.
Methodology and research
The names and approximate start markers follow the conventional ten-leap framework popularized by The Wonder Weeks. They are a chart convention, not scientifically established deadlines. This calculator selects the latest marker reached; it does not infer that a developmental phase lasts until the next marker.
Research on infant regressions and developmental transitions is mixed. Van de Rijt-Plooij and Plooij (1992) reported recurring regression periods in 15 mother-infant pairs. De Weerth and van Geert (1998) did not support a strictly timed pattern in a replication with four pairs. Sadurní and colleagues (2010) reported a relationship between regression and transition periods in 18 infants. These small studies do not establish the exact ten dates used here for individual babies.
For general skill tracking, visit the CDC developmental milestones. You can also explore the Baby Genetics Calculator or browse Pregnancy & Baby calculators.