Pregnancy Due Date Estimator
Enter the first day of your last period to estimate the due date, gestational age, and trimester.
When is the baby due?
The standard estimate uses Naegele’s rule: count 280 days — a full 40 weeks — from the first day of your last menstrual period. This tool applies that rule and also works out how far along you are today, in weeks and days, and which trimester that falls in.
It assumes a regular 28-day cycle with ovulation around day 14, the same assumption clinics start from before a dating scan refines it. Because only a small fraction of births land on the exact date, treat the result as a target window rather than a fixed day.
Private by design
Everything is calculated in your browser, so this sensitive information never leaves your device or reaches a server.
Frequently Asked Questions
How is the due date calculated?
By Naegele’s rule: the estimated due date is 280 days (40 weeks) from the first day of your last menstrual period. The tool also shows your current gestational age and trimester.
How accurate is it?
It assumes a regular 28-day cycle with ovulation on day 14. Only about 4% of babies arrive on the exact date; most come within two weeks either side. An ultrasound dating scan is more precise.
What if my cycle is not 28 days?
A longer or shorter cycle shifts ovulation, so the estimate drifts by the difference. Treat this as a guide and confirm with your provider.
Is my information private?
Yes. The dates are calculated in your browser and nothing you enter is uploaded or stored.
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