All Tools VersePregnancy Due Date Calculator
Estimate your due date from your last period or conception, with gestational age and trimester dates. Runs in your browser.
- Runs in your browser
- Nothing uploaded
- Free, no sign-up
Estimate your due date from your last menstrual period or conception date using Naegele's rule, and see how far along you are and when each trimester ends. Runs in your browser.
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| Milestone | Date |
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A full term pregnancy is about 40 weeks from the last period. Only about 1 in 20 babies arrive on the exact due date, so treat it as an estimate. Your doctor or midwife can confirm dates with an ultrasound.
How to Use Pregnancy Due Date Calculator
- Choose your starting point. Pick whether to calculate from your last menstrual period or your conception date.
- Enter the date. Add the date, and for the last period option set your average cycle length.
- Read your due date. See your estimated due date, how far along you are and which trimester you are in.
- Plan the milestones. Use the table for your conception estimate and the end of each trimester.
Frequently Asked Questions
How is the due date calculated?
This tool uses Naegele’s rule: it adds 280 days, about 40 weeks, to the first day of your last period, adjusted for your cycle length. From a conception date it adds 266 days.
How accurate is it?
It is a solid estimate, but only about 1 in 20 babies arrive on the exact due date. An early ultrasound gives the most accurate dating.
What if my cycle is not 28 days?
Enter your average cycle length and the tool shifts the due date accordingly, since ovulation and conception happen later in longer cycles.
What is gestational age?
It is how far along the pregnancy is, counted from the first day of your last period, shown here in weeks and days.
When do the trimesters change?
The first trimester runs through week 13, the second through week 27, and the third from week 28 to birth. The table lists your dates.
Is my information private?
Yes. All the calculations run in your browser and nothing you enter is uploaded or stored.
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