How far along am I?

Every method resolves to the same anchor, using ACOG's dating rules (Committee Opinion 700). Pregnancy is counted from the first day of your last period, and a due date is 280 days after it. So if you enter a last period, we adjust for your cycle length; a due date, we count back 280 days; a conception date, back 14 days; an ultrasound, we subtract the gestational age it reported from the scan date. From that single anchor, the tool counts the days to today and reports your exact weeks and days, trimester, percent complete, and every milestone date — all guaranteed to agree with each other.

Because gestational age — the number every clinician, app, and this page uses — is counted from the first day of your last menstrual period, not from conception. Ovulation and conception typically happen around two weeks after that, so the count starts roughly two weeks before a baby actually exists. It's a convention that predates ultrasound, and medicine has kept it because the period date is observable while the conception date usually isn't. Your baby's true age from conception (fetal age) is about two weeks less than your week number, and that's normal and expected.

The ultrasound — if the difference is big enough. ACOG's rule (Committee Opinion 700) is that an early scan is the most accurate dating method, and the pregnancy is redated to the scan when it disagrees with the period-based estimate beyond a threshold that grows with gestational age: more than 5 days up to 8w6d, more than 7 days from 9 weeks to 15w6d, more than 10 days at 16–21w6d, and larger gaps later. If your provider has already set a due date from an ultrasound, enter that due date (or the scan itself) here instead of your period — the scan-based date is your date of record.

This tool uses the divisions ACOG uses in its patient guidance: the first trimester runs through 13 weeks 6 days, the second from 14w0d through 27w6d, and the third from 28w0d to delivery. You'll see slightly different boundaries elsewhere (some sources hand over at 12 or 13 weeks) because trimesters are a communication convenience, not a biological switch — nothing changes in your body at midnight on the boundary. What actually drives your care is your precise week count, which is why the dashboard leads with weeks and days rather than the trimester label.

ACOG retired the old idea that anything from 37 weeks was simply 'term', because outcomes measurably improve week by week right up to 39. The official definitions: early term is 37w0d–38w6d, full term is 39w0d–40w6d, late term is 41w0d–41w6d, and postterm is 42 weeks onward. That's why a planned delivery without a medical reason waits for 39 weeks, and why being 'past your due date' at 40w3d is still entirely within the normal range. This page's dashboard flags each of those lines on your own calendar.

Completely. This tool runs entirely in your browser: the dates you enter are used on your own device and are never sent to a server, stored, or shared — close the tab and they're gone. We treat reproductive health data as sensitive by default, so there is no account, no tracking of your inputs, and nothing to delete. The result is an educational estimate based on published ACOG methods, not medical advice or a diagnosis; your provider and an early ultrasound are what confirm your dates.