Pregnancy
Due date, gestational age and a fertile window from the last period and cycle length.
Open a calculatorOvulation window
Ovulation is treated as cycle length minus 14 days after the first day of the last period. The fertile start is five days before that. The due date adds 280 days. Cycles wander. Not contraception and not a dating scan.
Estimated ovulation
2026-09-15
Fertile window starts
2026-09-10
Due date (280 days)
2027-06-08
Estimated ovulation: 2026-09-15
A 21-day cycle ovulates earlier than a 35-day one. The due date here ignores a dating scan.
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An educational estimate. Not medical, tax or credit advice.