Pregnancy Due Date Calculator
Estimate a due date from the last period, conception, IVF transfer or a scan.
Your Estimated Due Date, And The Weeks Before It
Pregnancy is counted from the first day of the last menstrual period — about two weeks before conception — and lasts around 280 days, or 40 weeks. That convention, Naegele’s rule, is what doctors and midwives use for the estimated due date, and it is the starting point here, adjusted for cycles longer or shorter than 28 days.
If you know the conception date, had an IVF transfer, or have had a dating scan, those give a more precise estimate and are all supported. Alongside the due date you will see how far along you are today, the trimester, and the dates of the usual milestones — screening windows, the anatomy scan, full term.
Key features
- Five methods — last period, conception, day-3 and day-5 IVF transfer, and dating scan.
- Cycle-length adjustment — for cycles from 20 to 45 days.
- Weeks and days today — with trimester and days remaining.
- Milestone dates — from screening windows to full term.
- Private — nothing is stored or sent anywhere.
This tool runs entirely inside your browser using native Web APIs. Your files and text are never uploaded to a server, never logged and never shared with third parties.
How to use: Pregnancy Due Date Calculator
- Choose the method
Last period is most common; a dating scan is the most accurate. - Enter the date
And your usual cycle length, or the age of the pregnancy at the scan. - Read your due date
With weeks and days today and the current trimester. - Check the milestones
Past milestones are dimmed; upcoming ones show their dates.
Technical specifications
| Processing location | Entirely in your browser — no server round trip |
|---|---|
| Data uploaded | None. Files and text never leave your device |
| Price | Free — no account, no trial, no usage cap |
| Category | Calculators |
| Works offline | Yes, once the page has loaded |
| Browser support | Chrome 90+, Edge 90+, Firefox 90+, Safari 15+ |
| Interface languages | English, 中文, हिन्दी, Español, العربية |
Frequently asked questions
How accurate is a due date?
It is an estimate. Only about one baby in twenty-five is born on its due date; most arrive within a week or two either side, and anywhere from 37 to 42 weeks is considered normal. A first-trimester dating scan is the most accurate way to set the date.
Why is pregnancy counted from my last period?
Because the first day of a period is a date most people know, while the exact day of ovulation and conception usually is not. Counting from the period adds about two weeks before conception, which is why a pregnancy is “40 weeks” although the baby develops for about 38.
How does IVF change the calculation?
With IVF the age of the embryo at transfer is known exactly. A day-5 blastocyst transfer gives a due date 261 days after the transfer; a day-3 transfer, 263 days.
What if my cycles are irregular?
Then the last-period method is less reliable, because ovulation may not have been around day 14. A dating ultrasound gives a much better estimate, and your midwife or doctor will usually use it.
Is this medical advice?
No. It uses the same standard formulas as a pregnancy wheel, but your midwife or doctor sets your official due date and should be your guide for everything in your care.