How many weeks and days pregnant you are today, and which trimester that falls in
Runs in your browser. Nothing you type is sent anywhere. Checked against sources on 29 Sept 2026.Pregnancy is counted in weeks and days from the first day of the last period, not from conception, which is why a scan at eight weeks describes an embryo about six weeks old. Enter that date to see today’s count, such as 22 weeks 3 days, the trimester on the ACOG lines at 14 and 28 weeks, and the calendar dates on which each later milestone falls.
Last period is already selected under "Method".
Enter the "First day of your last period" and your "Usual cycle length".
Read Today, shown as weeks and days, and the Trimester beside it.
Open Key dates to see the calendar date of each later milestone and which have passed.
A due date is a dating convention, not a forecast. The one most people are given comes from Naegele's rule: 280 days, or 40 weeks, from the first day of the last menstrual period. That rule assumes a 28-day cycle with ovulation around day 14, so this page moves the date by one day for every day your regular cycle runs longer or shorter than 28. A 32-day cycle gives a due date four days later.
Two other starting points are offered. From a known conception date the due date is 266 days on, the same 38 weeks with the two pre-ovulation weeks removed. After IVF, the American College of Obstetricians and Gynecologists (Committee Opinion No. 700) dates the pregnancy from the embryo's age at transfer: 263 days after a day-3 transfer and 261 days after a day-5 transfer.
Whichever you use, the page shows today's count in weeks and days, the trimester, the days left, and a table of milestones with their calendar dates. The trimester lines follow ACOG: the second begins at 14 weeks 0 days and the third at 28 weeks 0 days. Some bodies, including the NHS, draw them a week earlier, so a leaflet may disagree with this page by a week without either being wrong. The term labels come from ACOG Committee Opinion No. 579: early term from 37 weeks, full term from 39, late term from 41 and postterm from 42.
The rest of the article, and all 6 questions about Pregnancy Due Date Calculator, are on the Pregnancy Due Date Calculator page.
The first day of a period is a date most people know, while the day of conception usually is not. Counting from the period adds about two weeks before conception, so at 8 weeks pregnant the embryo is roughly 6 weeks old. Scans and antenatal notes use the same period-based count.
ACOG Committee Opinion No. 700 dates an IVF pregnancy from the embryo transfer. The due date is 263 days after transferring a day-3 embryo and 261 days after a day-5 blastocyst. A frozen transfer uses the same offsets, counted from the transfer date rather than from any period.
On the ACOG lines used here, the first trimester runs to 13 weeks 6 days, the second from 14 weeks 0 days to 27 weeks 6 days, and the third from 28 weeks 0 days. The NHS and some other sources start each trimester about a week earlier, so leaflets can differ.
ACOG Committee Opinion No. 579 labels a pregnancy early term from 37 weeks 0 days, full term from 39 weeks 0 days, late term from 41 weeks 0 days and postterm from 42 weeks 0 days. The milestone table on this page gives the calendar date on which each label begins.
Rates and rules change; check the source before you rely on a figure.
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