Due date calculator
Choose what you are counting from and enter the date to see the estimated due date and how far along the pregnancy is.
Count from
Estimated due date
Sunday 2 May 2027
Gestational age today
10+0
Week 11 of pregnancy
First trimester
Days to the due date: 210
Key dates
- Likely conception9 Aug 2026(passed)
- Second trimester begins (14+0)1 Nov 2026
- Third trimester begins (28+0)7 Feb 2027
- Full term (37+0)11 Apr 2027
- Estimated due date (40+0)2 May 2027
- Post-term (42+0)16 May 2027
Most babies are born between weeks 37 and 42. The date that counts is set by your midwife or doctor, usually after the dating scan.
How it works
Pregnancy is counted from the first day of the last period, not from conception. With a 28-day cycle, ovulation comes about two weeks later, so someone who is six weeks pregnant conceived about four weeks ago. The estimated due date is 280 days, or 40 weeks, after the first day of the last period.
If the cycle is longer or shorter than 28 days, ovulation moves and the due date moves by the same number of days. A 32-day cycle puts it four days later.
The dating scan early in pregnancy measures the baby and gives a more reliable date than the period, because ovulation varies. Maternity care usually goes by the scan date. Enter the gestational age you were given at the scan, such as 12+3, and the date is worked out from that.
With IVF the age of the embryo is known. An embryo transferred five days after fertilisation gives a due date 261 days after the transfer, and a three-day embryo 263 days.
Gestational age is written in completed weeks and days: 12+3 means twelve weeks and three days, which is the thirteenth week of pregnancy. The trimesters here change at 14+0 and 28+0.
A pregnancy is full term from 37+0 and post-term from 42+0. Only around four per cent of babies are born on the due date itself.
The calculation is an estimate and does not replace your midwife or doctor. Everything is worked out in your browser, and no dates are sent anywhere.