IUI Due Date Calculator

How IUI Due Dates Are Calculated

Pregnancy is conventionally dated from the first day of your last menstrual period (LMP), with a due date 280 days (40 weeks) later — but that assumes a standard cycle where ovulation happens on day 14. With IUI (intrauterine insemination), the insemination is timed to your actual ovulation, so your care team already knows your conception date precisely, without needing to estimate it from your cycle.

Because IUI happens right at ovulation — which in standard dating convention falls on "day 14," or 2 weeks pregnant — your due date works out to your IUI date plus 266 days (38 weeks) rather than the 280 days used for LMP-based dating. Both methods describe the same 40-week pregnancy; they just start counting from a different, equally valid reference point.

How to Use This Calculator

Enter the date of your IUI procedure. The calculator gives you your estimated due date along with a few commonly referenced milestones along the way, so you have a rough timeline for what's ahead.

How We Calculate It

Due date = IUI date + 266 days. Milestones are calculated the same way, working from standard LMP-convention gestational weeks minus the 14-day head start IUI dating gives you (milestone date = IUI date + milestone week × 7 − 14 days).

A Few Notes

Only about 5% of babies actually arrive on their exact estimated due date — it's a statistical midpoint, not a prediction, and a full-term delivery can happen anywhere from about three weeks before to two weeks after it. This calculator also assumes a single, successful implantation from the cycle you entered; your fertility clinic's own dating, especially after an early ultrasound, is more accurate than this or any calculator and should always take precedence.