Enter the first day of your last menstrual period and your usual cycle length to estimate your due date and how far along you are.
Pregnancy due date calculator
Estimated due date
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This calculator gives a general estimate for adults and is not medical advice. Talk to a doctor or a registered dietitian before making health decisions.
How it works
This uses Naegele's rule: the due date is 280 days (40 weeks) after the first day of the last period, adjusted by the number of days your cycle is longer or shorter than 28. Pregnancy weeks are counted from that first day, about two weeks before conception.
Only about 4% of babies arrive on their due date; most are born within two weeks either side of it. An early ultrasound scan gives a more accurate date and is what doctors and midwives normally use.
First trimester: weeks 1–13
Second trimester: weeks 14–27
Third trimester: week 28 to birth
Common questions
What if I do not know the date of my last period?
An ultrasound in the first trimester can date the pregnancy accurately. Ask your doctor or midwife.
Why does cycle length change the date?
Ovulation usually happens about 14 days before the next period, so longer cycles mean later ovulation and a later due date.