Due date and trimesters
Your due date is about 40 weeks after the first day of your last period. That is 280 days. Weeks 1 to 13 are the first trimester. Weeks 14 to 27 are the second. Week 28 on is the third.
Free pregnancy due date calculator
Pregnancy due date calculator by last period
Enter the first day of your last period. Your due date is about 40 weeks after that day. You also get trimester dates, a week count, days when pregnancy is more likely, and your next period date. This is calendar math only.
Not medical advice. This tool does calendar math only. It cannot tell you about your health. Talk to your doctor about your care.
Your calendar
Enter the first day of the last period, then press Calculate dates.
Reminder: calendar math only. This is not medical advice. Talk to your doctor for care that fits you.
What you get
Four results from one start date.
Week count
Pick any date to see how many weeks and days it is since your last period. Week 1 starts on your last period date.
Fertile window and next period
The fertile window means the days when pregnancy is more likely. We count it as five days before through one day after ovulation. Your next period is one full cycle after your last period.
Pregnancy due date questions
How is my due date figured out?
We add 280 days to the first day of your last period. That is about 40 weeks. Real due dates can shift with scan results, so use this as a start.
What if my cycle is not 28 days?
Type your usual length from 15 to 60 days. Your fertile window and next period shift with it. Your due date stays at last period plus 280 days.
Do leap years change anything?
No. The math counts exact calendar days. A start date of Feb 29 still lands right.
Can this tool say if something is wrong?
No. It does calendar math only. It cannot check your health. Call your doctor or a local care line with any worry.
Your dates stay with you.
This tool runs in your browser. It does not save your dates, send them anywhere, or use cookies. Your host still sees plain page requests, like any site.
Results are calendar math only. This is not medical advice, a diagnosis, or care advice. Talk to your doctor about your health.