Implantation Date Calculator: When Does Implantation Happen?

How it works

Ovulation = last period + (cycle length − luteal phase), or transfer date − embryo age for IVF · Implantation ≈ ovulation + 6 to 12 days, most often + 8 to 10, most likely + 9 · hCG in blood ≈ implantation + 2 days · Next period (reliable test) = ovulation + luteal phase (14) · Due date = ovulation + 266 days

After fertilisation, the embryo travels down the fallopian tube for several days and then attaches to the lining of the uterus. A landmark study that collected daily urine samples (Wilcox, Baird and Weinberg, New England Journal of Medicine, 1999) found that in pregnancies that continued, implantation happened 6 to 12 days after ovulation, and 84% of the time on day 8, 9 or 10. The calculator puts the most likely day at 9 days after ovulation and shows both the peak and the full window. The body starts making hCG only after implantation, which is why a pregnancy test taken before the missed period can be negative even when you are pregnant. If you know your ovulation, trigger shot or IUI date, the calculator starts from it. From a last period, it places ovulation at cycle length minus the luteal phase (14 days by default), which is less certain. For an IVF transfer, embryo age is subtracted from the transfer date to get the equivalent of ovulation day (day 0), so a day-5 blastocyst typically implants 1 to 7 days after transfer, most likely about 4 days after. It also gives the day a blood test can usually detect hCG, the date a home test is reliable (when your period is due), the due date if you are pregnant, and a day-by-day table with the early-loss rates the study found for each implantation day.

Worked example

With the defaults, ovulation was on Thursday, September 10, 2026. Implantation is most likely 9 days later, on Saturday, September 19, with the most common window Friday, September 18 to Sunday, September 20 and the full window Wednesday, September 16 to Tuesday, September 22. hCG could show in a blood test from about Monday, September 21; the next period is due and a home test is reliable from Thursday, September 24, 2026; and the due date if pregnant is Thursday, June 3, 2027.

Sources: Wilcox AJ, Baird DD, Weinberg CR. Time of implantation of the conceptus and loss of pregnancy. N Engl J Med 1999;340:1796–9 (abstract) · Omni Calculator: implantation calculator (ovulation + 9 days; ovulation = LMP + cycle − 14) · Cleveland Clinic: implantation bleeding (about 1 in 4 pregnancies, 10–14 days after ovulation)

Frequently asked questions