Conception Date Calculator
Estimate conception date and last menstrual period
Use this when you need a fast, accurate result — no sign-up, works entirely in your browser.
Estimated conception date—
Estimated last menstrual period—
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
- Estimated due date 2027-05-15 → Conception ≈ 2026-08-22, last period ≈ 2026-08-08
- Due date 2027-01-15 → Conception ≈ 2026-04-24; last period ≈ 2026-04-10
Formula
Full-term pregnancy is 40 weeks from the last menstrual period (LMP). Conception usually happens ~14 days after LMP, so conception date ≈ due date − 266 days.
About Conception Date Calculator
Estimate conception date and last menstrual period. 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.