Pregnancy Due Date Calculator
Free pregnancy due date calculator: from your last period, conception date, IVF transfer or ultrasound. See how many weeks pregnant you are, your trimester, days to go, key dates and a week-by-week calendar. Private, adds to your phone calendar.
🔒 Private by design: your dates are saved only in this browser (never uploaded, no account) and are shared by the three calculators below.
More options: period length, luteal phase, ovulation (LH) test
Your chances, day by day
Chance of pregnancy from sex on each day, for a typical couple. The two days before ovulation and ovulation day are the peak. Source: Wilcox, Weinberg & Baird, New England Journal of Medicine 1995 (129 couples, 625 cycles). Ovulation can move by a few days, which is why the whole window counts.
Your cycle log
Add the first day of each period you remember. With two or more, the calculator uses your own average instead of the textbook 28 days, and tells you how regular you are.
Upcoming periods
Calendar
Tap a day for details.
Next six cycles
Key dates
Week-by-week calendar (weeks 1–42)
Day by day after ovulation
Week by week
These are estimates from averages, not medical advice or contraception. Bodies vary and cycles change with stress, illness, breastfeeding and age. Talk to a doctor or midwife about your own situation, especially if your cycles are very irregular or you have been trying for 12 months (6 if you are over 35).
Pregnancy due date calculator
Work out your due date from the first day of your last period, the date of conception, an IVF embryo transfer (3-, 5- or 6-day embryos) or an ultrasound scan. You get today's gestational age in weeks and days, your trimester, days to go, a progress bar, key dates (heartbeat, anatomy scan, third trimester, full term) and a week-by-week calendar you can add to your phone.
How the due date is calculated
- Last period: add 280 days (40 weeks), adjusted if your cycle is longer or shorter than 28 days (Naegele's rule).
- Conception date: add 266 days (38 weeks).
- IVF transfer: add 261 days for a day-5 embryo, 263 for day 3, 260 for day 6.
- Ultrasound: 280 days minus the gestational age the scan reports on the scan date.
Questions
How accurate is a due date?
Only about 4 in 100 babies are born on their due date. Most arrive between 37 and 42 weeks. Your due date is the middle of that range, not a deadline. An early ultrasound (before about 14 weeks) is the most accurate way to date a pregnancy, and your midwife or doctor may move the date if the scan disagrees with your period dates by more than about a week.
Why is pregnancy counted from my last period and not from conception?
Because the date of the last period is usually known and conception is not. That is why you are already “2 weeks pregnant” on the day you ovulate.
When does each trimester start?
The first trimester runs to the end of week 13, the second trimester is weeks 14–27 and the third starts at week 28. The calculator shows the exact dates for your pregnancy.
What if I do not know when my last period was?
Choose “An ultrasound scan” and enter the scan date and the gestational age on the report. If you do not have a scan yet, ask your doctor or midwife for a dating scan.
Not trying yet? Use the ovulation calculator to find your fertile window.