Due Date Calculator
Estimated due date and trimester milestones
Use this when you need a fast, accurate result — no sign-up, works entirely in your browser.
Estimated due date (40 weeks)—
End of 1st trimester (13w)—
End of 2nd trimester (27w)—
How to Use
- Enter your details into the fields above.
- Click the calculate button to get your result instantly.
- Use the clear button to start a new calculation.
Example
- Last period 2026-08-20 → Due date ≈ 2027-05-27; 1st trimester end 2026-11-19
- Last period 2026-03-01 → Due ≈ 2026-12-06; T1 ends 2026-05-31, T2 ends 2026-09-06
Formula
Naegele's rule: due date = last period + 280 days (40 weeks). First trimester ends at 13 weeks, second at 27 weeks.
About Due Date Calculator
Estimated due date and trimester milestones. This free online tool gives you fast, accurate results without registration or downloads.
Everything runs locally in your browser, so your data is never uploaded or stored — privacy first.
Frequently Asked Questions
Is this tool free to use? +
Yes, it is completely free with no registration or download required.
Is my data private? +
Yes. Everything is processed locally in your browser. Nothing is uploaded or stored on our servers.
Does it work on mobile? +
Yes, it works on any device — phone, tablet, or desktop.