Pregnancy due date calculator
Find your estimated due date, how far along you are today, and the dates of key milestones.
Loading…
How your due date is estimated
Most due dates are counted from the first day of your last menstrual period (LMP). A typical pregnancy lasts 280 days, or 40 weeks, from that day. This is known as Naegele's rule. If your cycle is longer or shorter than 28 days, ovulation usually happens later or earlier, so the calculator moves the date by the difference.
- From conception: conception date + 266 days.
- IVF, day-3 transfer: transfer date + 263 days.
- IVF, day-5 transfer: transfer date + 261 days.
How accurate is a due date?
A due date is an estimate. Only about 1 in 20 babies is born on the exact day, and most arrive within two weeks either side. Doctors usually confirm or adjust the date with an ultrasound scan in the first trimester, which is the most accurate way to date a pregnancy.
The trimesters
Pregnancy is split into three trimesters: weeks 1 to 13, 14 to 27, and 28 until birth. A pregnancy is considered full term from 39 weeks.
This calculator gives an estimate only. Your doctor or midwife will confirm your due date.
Sources
Questions people ask
Why is pregnancy counted from my last period?
The first day of your last period is a date most people know, while the exact day of conception usually isn't. That's why the first two weeks are counted before conception happens.
My ultrasound gave a different date. Which is right?
Follow the date from your doctor or midwife. An early ultrasound is more accurate than a date based on your period.
What does full term mean?
A baby born between 39 weeks and 40 weeks 6 days is full term. From 37 weeks is early term.