Pregnancy Wheel
The classic clinician's gestational wheel, online. Enter your due date or last period to see exactly where you sit on the 40-week dial.
How this wheel is calculated
This is a digital version of the paper gestational calculator wheels used in prenatal clinics for decades. It's built on the same math behind Naegele's rule: a pregnancy is treated as 280 days (40 weeks) long, counted either from the first day of your last menstrual period, or backward from a known or estimated due date.
The colored ring marks the three trimesters — roughly weeks 0–13, 13–27, and 27–40 — and the marker's position shows how far around that 280-day dial you currently sit. It's a visual way to see the same week and trimester numbers you'd get from a due date calculator, just presented as a clock face instead of a list of stats.
Things to know
A wheel-based estimate assumes a textbook 28-day cycle with ovulation around day 14 — real cycles vary, and an early ultrasound is generally considered more accurate for dating than last-period math alone, especially if your cycles are irregular or you're not sure of your last period date.
Full term is generally considered 37–42 weeks, so "week 40" on the wheel is a target, not a guarantee — only a small share of babies actually arrive on their calculated due date. Always let your care provider's own dating take priority if it differs from what the wheel shows.
If you conceived through IVF or a frozen embryo transfer, or your cycles run notably longer or shorter than 28 days, a wheel built for the "average" cycle can be off by several days. In those situations, the date your clinic gives you from transfer day or a dating scan is a more reliable starting point than the last-period entry above.
Why clinics still use a wheel like this
Long before digital due-date calculators, paper gestational wheels let a clinician line up a last-period date and instantly read off a due date, current week, and trimester without doing the arithmetic by hand each visit. The format has stuck around because it's fast and visual: seeing "week 24" as a position on a dial, next to milestones like the anatomy scan or third-trimester visits, can be easier to picture than a raw number.
This online version keeps that same at-a-glance idea, while linking out to more detailed tools — the Due Date Calculator for a fuller breakdown, and the Weeks to Months Calculator if you'd rather think in pregnancy months.