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Due Date Calculator
Estimate your due date, current week, and trimester from your last period or a conception / IVF-transfer date. Private and free — nothing is saved unless you choose to.
How the due date calculator works
- How is my due date calculated?
- We use Naegele's rule — 40 weeks (280 days) from the first day of your last menstrual period, adjusted for your cycle length if you provide one. From a conception or IVF-transfer date, we count 266 days.
- How accurate is a due date estimate?
- It's an estimate: only about 1 in 20 babies arrive exactly on their due date, though most arrive within a week or so either side. A dating scan gives the most accurate estimate.
- Can I use a conception or IVF-transfer date?
- Yes. Switch the calculator to “Conception / IVF transfer” and enter that date — we count 266 days to your estimated due date.