How this calculator works
The calculator places your baby on the typical age windows for each commonly reported regression — around 4, 6, 8–10, 12, 15 and 18 months, and 2 and 3 years — and labels each window as likely behind you, possibly active now, or ahead (with the dates for your baby). The windows come from the same pediatric sleep guidance summarized across this site; see sources & methodology.
Two honest notes. First, these are typical ranges, not appointments — babies regularly run early, late, or skip a window entirely. Second, the calculator can't see your baby: a rough patch outside a window, or a smooth ride through one, are both completely normal.
Born early? Use corrected age
For babies born more than about three weeks early, development tracks the due date more closely than the birth date in the first couple of years. Tick the corrected-age box and the whole timeline shifts to match — a baby born eight weeks early will typically meet the 4-month regression around six months on the calendar.
What to do with the answer
- In a window now? Open the linked age guide for exactly what's driving this stage and what helps.
- Window approaching? Nothing to dread — but it's a good moment to tighten the bedtime routine and check wake windows, so the foundation is solid before the turbulence.
- Just left one? Now is the time to gently retire any emergency habits (the 3 a.m. feeds-back-to-sleep, the hand-holding) before they set.
Frequently asked questions
How accurate is the sleep regression calculator?
It reflects the typical age windows reported in pediatric sleep guidance, adjusted to your baby's exact birthdate (or corrected age). It describes probability, not certainty — babies run early, late, or skip windows entirely.
Does it work for premature babies?
Yes — tick the corrected-age option and enter how many weeks early your baby arrived. The timeline then counts from the due date, which tracks development better in the first two years.
Where do the age windows come from?
From the commonly reported regression ages in pediatric sleep resources — summarized with citations on our sources and methodology page.
Is my data stored?
No. The calculator runs entirely in your browser — the birthdate never leaves your device and nothing is saved.
My baby is waking badly outside every window — is something wrong?
Not necessarily; sleep disruption has many ordinary causes (teething days, illness, schedule drift, travel). If waking persists for weeks or comes with fever, breathing changes or feeding problems, check with your pediatrician.
Can I put this calculator on my website?
Yes — we offer a free embeddable version for parenting blogs, daycare sites and newsletters. See the embed page for the copy-paste code.
- American Academy of Pediatrics — HealthyChildren.org: baby sleep
- NHS — Helping your baby to sleep
- Cleveland Clinic — Sleep regressions
Full editorial approach: sources & methodology.