Pregnancy due date calculator
Our free online due date calculator finds your due date, how many weeks pregnant you are today and every key milestone in between. Start from whichever date you know best.
What date do you know?
Enter the date
Dates stay in your browser. We never receive them.
Your pregnancy milestones
Get weekly emails- Conception — Week 2
- Missed period, test day — Week 4
- First prenatal visit — Weeks 8 to 10
- Second trimester begins — Week 13
- Anatomy scan — Weeks 18 to 22
- Third trimester begins — Week 28
- Full term — Week 39
- Due date — Week 40
More pregnancy calculators
See all pregnancy calculatorsHow the dates are worked out
How many weeks pregnant am I?
Pregnancy is counted from the first day of your last period, so the week you are in is the number of days since that date divided by seven. If your period started 31 days ago you are 4 weeks and 3 days pregnant. The calculator above does this for you and shows your trimester, so it doubles as a weeks pregnant calculator.
- From your last period. Count the days since the first day, then divide by 7. The whole number is your weeks and the remainder is the extra days.
- From your conception date. Add 2 weeks, because you count as two weeks pregnant on the day you conceive.
- From your due date. A full pregnancy is 40 weeks, so take the weeks left until your due date away from 40.
- From an ultrasound. The scan report gives the weeks and days on the day of the scan, and your provider may move your due date to match.
To work the other way, our conception calculator finds when you most likely conceived from your last period or due date, and the hCG calculator estimates the weeks from a blood test result. Our week by week pregnancy guides explain each week from 1 to 40.
Common questions
Still unsure about your dates? Your first ultrasound gives the most accurate estimate.
How many weeks pregnant am I?
Enter the first day of your last period above to see your weeks and days today. By hand, count the days since that date and divide by 7, or add 2 weeks to the weeks since your conception date.
How accurate is a due date calculator?
It gives an estimate from a 280-day pregnancy counted from your last period. Only a small share of babies arrive on the due date, so treat it as the middle of a window of a few weeks. An early ultrasound can move the date.
How do I work out my conception date from my due date?
Count back 266 days, which is about 38 weeks, from your due date. The conception calculator on our home page does the counting and shows a window of a few days either side.
Why does my doctor count from my last period?
Most people know that date, so it is the standard starting point. That is why you are considered two weeks pregnant at conception.
Can an ultrasound change my due date?
Yes. An early scan measures your baby and may move your due date if it differs from your period-based date by more than a few days.
What if my cycles are irregular?
Use the due date from your scan if you have one, since it skips cycle length entirely. Otherwise your provider can help you work out the best estimate.
How many babies arrive on their due date?
Only a small share. Most babies arrive in the weeks around it, so think of your due date as the middle of a due window.
