Pregnancy Due Date Calculator
Find your due date and how far along you are from your last period, conception, an IVF transfer or a scan.
Today, Oct 28, you are 11 weeks 2 days pregnant, in the first trimester, 201 days before the due date.
Your pregnancy timeline
The pregnancy is counted from Aug 10, 2026. Trimester 1 runs to Nov 15, trimester 3 starts Feb 22, and the due date at 40 weeks is Mon, May 17, 2027. The marker is Wed, Oct 28, 2026: 11 weeks 2 days, first trimester. Ticks under the bar are the milestones in the table below.
Working
- 1Period-equivalent date: last period moved by your cycle length minus 28 daysAug 10 + 0 days = Aug 10
- 2Due date: 280 days (40 weeks) laterAug 10 + 280 days = May 17
- 3How far along todayOct 28 − Aug 10 = 79 days = 11w 2d
- 4Check: 40 weeks back from the due date gives the start dateMay 17 − 40 weeks = Aug 10
Milestones and screening windows
| Date | Milestone | |
|---|---|---|
| 10w | Mon, Oct 19, 2026 | Cell-free DNA (NIPT) screening available from |
| 11w | Mon, Oct 26, 2026 | First-trimester screening window opens (11 to 13 weeks) |
| 13w 6d | Sun, Nov 15, 2026 | End of the first trimester |
| 18w | Mon, Dec 14, 2026 | Anatomy ultrasound window (18 to 22 weeks) |
| 24w | Mon, Jan 25, 2027 | Glucose screening for gestational diabetes (24 to 28 weeks) |
| 27w | Mon, Feb 15, 2027 | Tdap vaccine window opens (27 to 36 weeks) |
Dates count from Aug 10, 2026. Screening windows are when tests are usually offered; your care team sets the exact day.
Trimesters and term
- First trimester (to 13w 6d)ends Nov 15
- Second trimester (14w 0d to 27w 6d)
- Third trimester (from 28w 0d)from Feb 22
- Early term (37w 0d to 38w 6d)from Apr 26
- Full term (39w 0d to 40w 6d)from May 10
- Late term (41w 0d to 41w 6d)from May 24
- Post-term (42w 0d or more)from May 31
Term categories: ACOG Committee Opinion 579 (2013). The highlighted row is the date checked above.
Check against your scan
If a dating scan gave a different age, enter it. The tool compares the two due dates with the ACOG redating rule.
The scan puts your due date 2 days later. For a scan at 9w 0d to 15w 6d by your period, ACOG suggests redating only when the gap is more than 7 days, so the period date usually stands.
Redating gaps: ACOG Committee Opinion 700 (2017), table 1. Your clinician makes the final call.
If your cycle is shorter or longer
- 25-day cycle
- Fri, May 14, 2027
- 26-day cycle
- Sat, May 15, 2027
- 27-day cycle
- Sun, May 16, 2027
- 28-day cycle (yours)
- Mon, May 17, 2027
- 29-day cycle
- Tue, May 18, 2027
- 30-day cycle
- Wed, May 19, 2027
- 31-day cycle
- Thu, May 20, 2027
Each extra day of cycle moves the due date one day later, because ovulation comes later in a longer cycle.
Before you rely on this result. This tool is for education only and is not medical advice. Clinical decisions must be made by a qualified health professional using the full clinical picture. Sources used on this page.
How it's worked out
Doctors count a pregnancy from the first day of your last period, not from conception. That date is easy to know, and it sits about two weeks before you ovulate. So on the day you conceive, you are already counted as two weeks pregnant. A full pregnancy is 40 weeks, or 280 days, from that start date:
This is Naegele's rule. It assumes a 28-day cycle with ovulation on day 14. If your cycle is longer, you ovulate later, so the start date moves by your cycle length minus 28. A 33-day cycle moves it five days later.
The other methods all work back to the same start date first:
- Conception: subtract 14 days.
- IVF, day-5 transfer: subtract 19 days (the embryo is 5 days old, plus 14). Day-3 transfer: subtract 17 days.
- Scan: subtract the age the scan measured, such as 12 weeks 2 days.
- A due date you were given: go back 40 weeks. This lets you see how far along you are on any date.
Your week number on a date is the days since the start date, split into whole weeks and leftover days. Trimester 1 ends at 13 weeks 6 days, and trimester 3 starts at 28 weeks.
Worked examples
Lena: a regular 28-day cycle
Lena's last period began Aug 10, 2026. Adding 280 days puts her due date on Mon, May 17, 2027. Conception most likely happened around Aug 24. Her baby counts as full term from May 10, 2027, and early term from Apr 26.
Priya: an IVF day-5 transfer
Priya's clinic transferred a 5-day embryo on September 3, 2026. Going back 19 days gives a start date of Aug 15, 2026, so she is due Sat, May 22, 2027. That is the same date a period on Aug 15 would give (May 22). Her clinic's date comes from the embryo's age, so a later scan will not move it.
Dana: a long cycle and a scan that disagrees
Dana's last period began July 1, 2026, and her cycles run 33 days. That moves her start date to Jul 6 and her due date to Mon, Apr 12, 2027. With the usual 28 days, she would have been told Apr 7. On September 16 her scan measured 9 weeks 1 day, while her period said 10 weeks 2 days. The scan puts her due date at Tue, Apr 20, 2027, 8 days later. A gap over 7 days at this stage is enough for doctors to switch to the scan date.
Reading your result
Treat your due date as the middle of a window, not a deadline. Only about 4 to 5% of babies arrive on it. In a 2013 study that pinned down the exact day of ovulation, natural pregnancy length still varied by about five weeks. First babies tend to come a little later.
The ACOG term definitions name each part of that window:
| Stage | Weeks |
|---|---|
| Early term | 37w 0d to 38w 6d |
| Full term | 39w 0d to 40w 6d |
| Late term | 41w 0d to 41w 6d |
| Post-term | 42w 0d or more |
An early scan is the most accurate way to date a pregnancy. ACOG Committee Opinion 700 sets how big a gap between your period date and the scan date should be before the due date changes. The allowed gap grows later in pregnancy, because babies grow at different rates:
| Age at the scan | Change the date if the gap is over |
|---|---|
| Up to 8w 6d | 5 days |
| 9w 0d to 15w 6d | 7 days |
| 16w 0d to 21w 6d | 10 days |
| 22w 0d to 27w 6d | 14 days |
| 28w 0d or more | 21 days |
Once a scan has set your date, it should not keep moving with each later scan. A baby measuring big or small at 30 weeks is a growth question, not a dating one.
Common mistakes
- Counting from the last day of your period. Day 1 is the first day of real bleeding. Starting from the end moves your due date about five days too late.
- Ignoring a long or short cycle. With a 35-day cycle, the plain 280-day rule puts your due date a week too soon. Enter your usual cycle length.
- Using conception and adding 280 days. From conception the count is 266 days. Adding 280 makes you two weeks later than you are.
- Mixing up the IVF transfer days. A day-5 embryo is two days older than a day-3 one, so it subtracts 19 days, not 17.
- Reading weeks pregnant as months. 40 weeks is about nine months and one week, and calendar months do not line up with weeks. Use weeks when you talk with your midwife or doctor.
Questions people ask
Sources
- ACOG Committee Opinion 700: Methods for Estimating the Due Date (2017)
- ACOG Committee Opinion 579: Definition of Term Pregnancy (2013)
- ACOG Committee Opinion 797: Prevention of Group B Streptococcal Early-Onset Disease in Newborns (2020)
- Jukic, A. M. et al. (2013). Length of human pregnancy and contributors to its natural variation. Human Reproduction 28, 2848-2855
Maintained by Anil ShahUpdated October 28, 2026Checked against 9 reference values