How to use the Pregnancy Due Date Calculator
- Choose what date you know.
- Pick the date, and for LMP your usual cycle length.
- Press Calculate.
Formula
Naegele’s rule: due date = first day of LMP + 280 days, adjusted by (cycle length − 28) days.
From conception: + 266 days. From IVF transfer: + 263 days (day-3 embryo) or + 261 days (day-5 blastocyst).
Examples
- LMP 1 March 2026, 28-day cycle → due date 6 December 2026.
Frequently asked questions
How accurate is the due date?
It is an estimate. A first-trimester ultrasound measurement is usually the most accurate way to date a pregnancy.