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Pregnancy Due Date Calculator

প্রেগন্যান্সি ক্যালকুলেটর

Find your due date from the first day of your last period, or how many weeks pregnant you are from your doctor’s due date, with trimester and term dates.

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I know

Today by default.

Nothing you enter is saved or sent anywhere, and this calculator keeps no history.

Your due date will appear here

Enter a date, then select Calculate due date.

How the due date is calculated

Due date = first day of your last period + 280 days (40 weeks)

Pregnancy is counted from the first day of the last period, not from conception, because that first date is usually known. How many weeks pregnant you are is the number of days since then ÷ 7: completed weeks and the days left over.

Worked example

  1. The last period started on 1 June 2026.
  2. 1 June 2026 + 280 days = 8 March 2027 (a Monday), the due date.
  3. On 1 November 2026 it is 153 days since 1 June: 153 ÷ 7 = 21 weeks with 6 days over, so 21 weeks 6 days.
  4. 21 weeks is the second trimester, with 127 days to the due date.

If your doctor gave you a date from an ultrasound, choose “Due date from my doctor”. The calculator counts 280 days back from that date and shows how many weeks you are now. For a due date of 20 May 2027, on 1 November 2026 that is 11 weeks 3 days, in the first trimester.

Trimesters and term

StageWeeks
First trimesterUp to 13 weeks 6 days
Second trimester14 weeks to 27 weeks 6 days
Third trimester28 weeks until birth
Early term37 weeks to 38 weeks 6 days
Full term39 weeks to 40 weeks 6 days
Late term41 weeks to 41 weeks 6 days
Post-term42 weeks and later

The due date falls at exactly 40 weeks, in the middle of full term. Think of it as the middle of a window, not a fixed day.

When your doctor’s date is more accurate

  • A first-trimester ultrasound is more accurate than the period date. ACOG’s guidance says to use the ultrasound date when the two differ.
  • Irregular periods, or not being sure of the date of the last period, make the 280-day rule less accurate. Many websites add or subtract days for cycle length, but we found no authoritative source for that, so we don’t.
  • After IVF the date is worked out from the embryo transfer; use the date your doctor gave you.

What this calculator is not

This calculator only works out dates; it is not medical advice and doesn’t replace antenatal check-ups. The World Health Organization recommends at least eight contacts with a health worker during pregnancy. If anything worries you, contact a doctor or your nearest health centre.

The BMI Calculator doesn’t apply during pregnancy; ask your doctor about your weight before pregnancy. To count the days between any two dates, use the Date Difference Calculator.

How to use the calculator

  1. Choose “First day of my last period” or “Due date from my doctor”.
  2. Enter the date. The date to count to is today by default; you can change it.
  3. Select Calculate due date to see the weeks, due date, trimester, days to go and the date each stage of term starts.

The dates you enter are never sent anywhere. For privacy, this calculator also keeps nothing in “Your recent calculations”.

Sources

Checked on 1 November 2026.

Frequently asked questions

How is the due date calculated?

By convention, the due date is 280 days (40 weeks) after the first day of your last menstrual period, as in ACOG’s guidance on estimating the due date. For example, a last period that started on 1 June 2026 gives a due date of 8 March 2027.

How many weeks pregnant am I?

Count the days from the first day of your last period and divide by 7. With a last period on 1 June 2026, on 1 November 2026 that is 153 days: 21 weeks and 6 days, in the second trimester, with 127 days to the due date.

My doctor gave a different due date. Which is right?

Go by your doctor’s date. A first-trimester ultrasound is more accurate than the period date, and ACOG says a due date set by early ultrasound (or by IVF dates) should be used. Choose “Due date from my doctor” to see your weeks from that date.

Why is pregnancy counted from the last period, not from conception?

Because the first day of the last period is usually known, while conception isn’t. In a typical 28-day cycle conception happens about two weeks later, so the count includes about two weeks before conception. Doctors and this calculator count the same way.

What are the trimesters?

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.

Will the baby be born on the due date?

The due date is an estimate, not an appointment. ACOG calls birth from 37 weeks “early term”, from 39 weeks to 40 weeks 6 days “full term”, 41 weeks “late term” and from 42 weeks “post-term”. The calculator shows the date each one starts.

My periods are irregular. Will this still work?

Less well. The 280-day rule assumes a regular cycle, and we don’t adjust for cycle length because we found no authoritative rule for it. An early ultrasound gives a more reliable date; enter that date with “Due date from my doctor”.

Is what I enter saved anywhere?

No. The dates stay on your phone or computer and are never sent anywhere. Unlike our other calculators, this one doesn’t keep a list of recent calculations, so nothing about a pregnancy is left on a shared device.

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