Due Date Calculator
Estimate your pregnancy due date, how many weeks along you are, and your trimester dates from your last period.
Due date is estimated as 280 days (40 weeks) after your last period, using Naegele's rule.
Estimated due date
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- How far along
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- Current trimester
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- Est. conception
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- Days until due
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Trimester timeline
- 1st trimesterWeeks 0–13—
- 2nd trimesterWeeks 14–27—
- 3rd trimesterWeeks 28–40—
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How to use it
- 1
Choose a method
Use the first day of your last period (most common) or, if you know it, your conception date.
- 2
Pick the date
Select the date on the calendar. Everything recalculates instantly in your browser.
- 3
Read your results
See your estimated due date, how many weeks along you are, your trimester dates, and days to go.
Perfect for every need
Plan ahead
Get an estimated due date early so you can plan appointments, leave, and preparations.
- Maternity leave dates
- Appointment planning
- Countdown to birth
Track your progress
See how many weeks and days pregnant you are today and which trimester you are in.
- Weeks pregnant
- Trimester dates
- Gestational age
Understand the timeline
See the date ranges for each trimester and roughly when conception was estimated to occur.
- Estimated conception
- First-trimester dates
- Third-trimester start
Frequently asked questions
How is the due date calculated?
It uses Naegele's rule: the estimated due date is 280 days (40 weeks) after the first day of your last menstrual period. If you enter a conception date instead, the due date is estimated as 266 days later.
What does 'how many weeks pregnant' mean here?
Gestational age is measured from the first day of your last period, not from conception. So the number of weeks and days shown is today's date minus that starting date, which is the standard way pregnancy is dated.
How are the trimesters defined?
This tool uses weeks 0–13 for the first trimester, weeks 14–27 for the second, and weeks 28–40 for the third, then shows the matching date ranges based on your start date.
Is this an exact date?
No. This is an estimate for general information only and not medical advice. Only about 1 in 20 babies arrive on their due date, and cycles vary between people. Always confirm your dates and any decisions with your doctor or midwife.