Upcoming milestones
Run the calculation to see the next milestones.
Pregnancy calculator
Calculate pregnancy weeks and due date from LMP, conception, or ultrasound. Shows trimester, days remaining, and key dates.
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- Select a method to get started.
Twin pregnancies often deliver earlier than 40 weeks. Expect closer monitoring.
Guidance by country
Choose a country to surface typical screening windows, scans and vaccines (non-clinical information).
Pick a country from the advanced options.
Week-by-week calendar
| Week | Start | End |
|---|---|---|
| Enter your data to generate the calendar. | ||
How we estimate gestational age
Choose the starting point that matches your data. With the last menstrual period we adjust the count using your average cycle length before applying Naegele’s rule (280 days). If you know the conception date we add the usual two weeks between LMP and ovulation and count 266 days from there.
For ultrasounds you can enter the gestational age reported in the scan or a crown–rump length between 5 and 84 mm. We convert CRL to days with the Fetal Medicine Foundation chart and, when the scan differs from the LMP by more than five days, the ultrasound takes precedence. You can also compare an additional scan from the advanced options.
The calculator builds a prenatal calendar with common checkpoints (screening, anomaly scan, glucose test, vaccines) based on the country you select. Everything runs locally in your browser; it is informative only and does not replace personalised medical advice.
Why is the estimated due date not exact?
It is calculated by adding 280 days to the adjusted LMP or 266 days to conception. It remains an estimate: the actual birth may happen earlier or later and only your care team can refine it.
What if my cycles are very irregular?
You can enter your average cycle length. If the variation is large, a first-trimester ultrasound usually provides the most reliable dating.
Does it work after assisted reproduction?
Yes. Use the fertilisation or embryo transfer date as conception. For blastocyst transfers you can add five days to the egg retrieval date to compare.
Do you store the information I enter?
No. All calculations run locally in your browser and nothing is sent to our servers.
