Pregnancy Week Calculator
Find your current gestational age in weeks and days. Enter your estimated due date or the first day of your last period.
What do you know?
Your estimate
Enter a date to see your pregnancy week.
How gestational age is calculated
Pregnancy is usually dated from the first day of the last period. A typical pregnancy is described as 40 weeks, or 280 days. If you enter a due date, the calculator works backward from that date; if you enter a last period date, it counts forward from that date.
Trimesters are shown using common boundaries: the first trimester through 13 weeks and 6 days, the second through 27 weeks and 6 days, and the third from 28 weeks onward.
For the full method and the role of ultrasound dating, read how pregnancy due dates are calculated.
What this tool cannot tell you
- Whether the pregnancy is developing as expected
- Your baby’s health or size
- When you will give birth
- Whether your dating is correct
Your care team’s dating may differ, especially after an ultrasound. Use their information for medical decisions.
Questions about pregnancy weeks
How do I know how many weeks pregnant I am?
Count from the first day of your last period, or use the due date your care team gave you. This calculator shows the result in weeks and days, which is how gestational age is usually described.
What if I do not know my last period date?
Enter your estimated due date instead. An early ultrasound can provide a due date when the last period date is uncertain. Ask your care team if you are not sure which date to use.
Why does another app show a different week?
Apps may count from a different starting point or use a different due date. A difference of a few days is common. For medical decisions, use the dating provided by your maternity care team.
General references
These organizations provide general health information. They are external sites with their own content and policies, and this site is not affiliated with them.