Rex says
Same equations the textbooks use — just way less awkward. Pop in your stats and I'll tell you what the number actually means for you.
Try a scenario
Click to load — tweak from there.Inputs
Result
Estimated due date
2027-02-24
Current week
0
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter first day of last period.
- 2Read your estimated due date on the right — it updates as you type.
- 3Hit Share to keep the scenario or send it to someone.
About this calculator
Naegele's rule: due date is the first day of the last menstrual period + 280 days.