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Pregnancy Week Calculator

Pregnancy week calculator tells you how many weeks and days pregnant you are today, or on any date you pick, with your trimester, due date and the dates of the weeks ahead.

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What this tool does

How many weeks pregnant am I? Weeks and days, trimester and due date from your last period, IVF transfer or scan, on today or any date. Nothing is uploaded.

How to use it

  1. Under Work it out from, choose Last period, Conception, IVF transfer, Ultrasound or a Due date you already have.

  2. Pick the date, and the cycle length, embryo day or scan weeks if asked.

  3. Tap Calculate due date. The page shows how many weeks and days pregnant you are today, your trimester, the days left and the due date.

  4. To check a future date, such as a trip or an exam, change Show the weeks on in More options. The weeks update at once.

Common uses

Pregnancy weeks are counted from the first day of your last period, not from conception, and a full pregnancy is 40 weeks or 280 days. Doctors write the age as weeks plus days, for example 9 weeks 5 days, often shortened to 9w5d or 9+5. If your last period started on 15 August 2026, on 22 October 2026 you are 9 weeks 5 days pregnant, in the first trimester, with 212 days to the due date of 22 May 2027.

Because the count starts at the period, the baby's age from conception is about two weeks less than the pregnancy week. The page shows the likely conception date too. If you know your conception date or had IVF, choose that method instead: conception adds 266 days to reach the due date, and ACOG dates an IVF pregnancy 261 days from a day-5 transfer or 263 days from a day-3 transfer.

If you already have a due date from your doctor, choose Due date and pick it. The weeks are then counted back from that date, so they match your scan reports and antenatal card exactly. This is the best choice once an early scan has set your date, because ACOG advises that a due date set that way should rarely change.

Trimesters follow the usual split. The first trimester runs to 13 weeks 6 days, the second from 14 weeks to 27 weeks 6 days and the third from 28 weeks until birth. A black bar shows how far you are through 40 weeks with marks at 14 and 28 weeks, and the timeline below lists the dates when each new stage begins, along with the WHO checkup weeks (by 12, then 20, 26, 30, 34, 36, 38 and 40) and the term dates from 37 weeks.

Show the weeks on lets you look ahead or back. Planning travel, leave or a family event? Pick that date and see the week and trimester on that day. Pick a past date to find out how far along you were at a scan or test.

Private, and the limits

The dates never leave your browser. TaskNinja does not receive, store or log them, and there is no sign-in. Only anonymous usage counts are recorded, never your dates.

Weeks from a period date are an estimate. If an early scan gave a different age, choose Ultrasound or Due date so the weeks match what your doctor uses. Speak to your doctor or midwife about anything that worries you.

Official sources

Last checked 2026-10-22.

FAQ

How many weeks pregnant am I?
Count the days from the first day of your last period to today and divide by 7. The weeks are the whole number and the remainder is the days. The calculator does this for you, adjusted for your cycle length.
What does 12+3 or 12w3d mean?
12 weeks and 3 days pregnant, counted from the first day of your last period. Scan reports and antenatal cards use this format.
How many months pregnant is 20 weeks?
About four and a half months. Doctors count in weeks because months have different lengths. 40 weeks is about nine calendar months and one week.
When does the third trimester start?
At 28 weeks 0 days. The second trimester starts at 14 weeks 0 days. The timeline on this page gives the exact date of each for your pregnancy.
Is my week different from my baby's age?
Yes. The pregnancy week counts from your last period, about two weeks before conception, so the baby's age from conception is about two weeks less.

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