Pregnancy Due Date Calculator

The Pregnancy Due Date Calculator is a free online tool that calculate your estimated due date using last menstrual period, conception date, or ultrasound. shows current gestational age, trimester, and prenatal milestone timeline.. It runs entirely in your browser with no installation or sign-up needed.

Naegele rule: LMP + 280 days (40 weeks). Adjusted for cycle length if different from 28 days. Conception method uses +266 days; ultrasound method back-calculates from measured gestational age.

First-trimester ultrasound is the gold standard, accurate to ±5-7 days. LMP dating is accurate to ±2 weeks when cycles are regular. Conception dating is accurate if you know exactly when conception occurred.

Only about 4% of babies are born on their exact EDD. Most arrive within 2 weeks before or after (37-42 weeks = full term). Your provider may adjust the EDD after the first ultrasound.

Yes, the Pregnancy Due Date Calculator is 100% free with no registration, no hidden fees, and no usage limits. All processing happens locally in your browser, ensuring complete privacy.

Absolutely. The Pregnancy Due Date Calculator processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the Pregnancy Due Date Calculator is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the Pregnancy Due Date Calculator in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

The Pregnancy Due Date Calculator works in all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience, use the latest version of your preferred browser.

Pregnancy is counted in 40 weeks from the first day of your last menstrual period (LMP), so your current week is the time elapsed since that LMP, not since conception. If you only know your due date, subtract 280 days from it to find the equivalent LMP, then count forward to today. For example, a due date eight weeks away puts you at roughly 32 weeks, because 40 minus 8 equals 32. Clinicians always express this as completed weeks plus extra days, like "32w 4d," rather than rounding up. This tool does the math for you: enter your LMP, conception date, or ultrasound result and it instantly shows your gestational age in weeks and days, your trimester, and how many days remain until your estimated due date.

Your due date can shift because LMP dating assumes you ovulated on day 14 of a textbook 28-day cycle, which often isn't true. If you ovulated earlier or later, or aren't certain of your last period, the LMP estimate drifts. A first-trimester ultrasound measures the embryo directly and is accurate to within about 5 to 7 days, so providers commonly re-date the pregnancy when the scan disagrees with the LMP by more than roughly a week. This is normal and makes later screening tests more reliable. You can see both estimates side by side here: calculate once with your LMP, then switch to the ultrasound method and enter the gestational age your sonographer measured to compare how much your due date moves.

Standard Naegele's rule adds 280 days to your LMP assuming a 28-day cycle with ovulation on day 14. If your cycle is longer or shorter, ovulation and conception happen on a different day, so the textbook formula can be off by several days. The fix is to adjust for the difference: a 32-day cycle ovulates about four days later, pushing the due date roughly four days back, while a 24-day cycle pulls it forward. This calculator handles that automatically. Choose the LMP method, enter the first day of your last period, then set your real cycle length anywhere from 20 to 45 days, and the estimated due date shifts to match your actual ovulation timing rather than the generic 28-day assumption.

Several key checkpoints map to specific gestational weeks. A missed period and positive test usually appear around week 4, the first prenatal visit near week 8, and the end of the first trimester at week 12. The anatomy scan, where the baby's sex can often be seen, falls around weeks 18 to 20, glucose screening near week 24, and the third trimester begins at week 28. Weekly visits typically start at week 36, full term begins at week 37, the estimated due date lands at week 40, and post-term induction is usually discussed around week 42. This tool plots all thirteen of these milestones against your own calendar dates and marks each as passed or upcoming, so you can see exactly when each one arrives.

Yes, you can work backward, though the result is an estimate rather than an exact day. Conception typically occurs about 266 days, or 38 weeks, before the due date, because the standard 40-week count is measured from your last period roughly two weeks before you actually ovulated. So subtracting 266 days from your estimated due date gives an approximate conception window. Keep in mind sperm can survive several days, so the precise day of fertilization is rarely certain unless you tracked ovulation closely. If you already know your conception date, this calculator works in the other direction too: pick the conception method, enter that date, and it adds 266 days to show your estimated due date, current week, and trimester.