Implantation Calculator
Implantation happens 6 to 12 days after ovulation, most often around day 9.
Your ovulation date
Implantation window
To see how many days past ovulation you are today, use the DPO calculator.
Why testing early gives a false negative
After fertilisation the embryo takes several days to travel down the fallopian tube and attach to the uterine lining. Implantation occurs 6 to 12 days after ovulation, most commonly around day 9, and the timing genuinely matters: research has found that later implantation is associated with a higher rate of early pregnancy loss.
hCG — the hormone pregnancy tests detect — is only produced after implantation, and then takes a couple of days to reach detectable levels, roughly doubling every 48 hours. This is the entire explanation for why testing early returns a negative on a genuinely pregnant person. Testing at 8 days past ovulation, before implantation has even occurred in many cycles, cannot work no matter how sensitive the test.
Implantation bleeding — light spotting around the expected implantation window — occurs in roughly a quarter of pregnancies, which means its absence says nothing at all, and its presence is easily confused with an early period. Some people also report a brief dip in basal body temperature around implantation, though this is not a reliable indicator on its own.
Medical disclaimer. This calculator is for general information and education only. It is not medical advice, not a diagnosis, and not a substitute for professional care. Timing varies between cycles and individuals, and pinpointing ovulation is itself imprecise unless tracked with ovulation tests or ultrasound.Speak to a doctor or another qualified clinician about any health decision.Last reviewed .
Frequently asked questions
When does implantation happen?
Between 6 and 12 days after ovulation, most commonly around day 9. Implantation later in that window is associated with a higher rate of early pregnancy loss.
Why does testing early give a negative?
Because hCG is only produced after implantation, and then takes a couple of days to reach detectable levels. Testing before implantation has occurred cannot produce a positive regardless of how sensitive the test is.
What is implantation bleeding?
Light spotting that occurs around implantation in roughly a quarter of pregnancies. Its absence means nothing, since most pregnancies show none, and it is easily mistaken for the start of a period.
When is the earliest reliable pregnancy test?
Around 12 to 14 days after ovulation, which is roughly the date of a missed period. Some sensitive tests detect hCG a day or two earlier, but a negative before that point is uninformative rather than reassuring.
How do I know when I ovulated?
Ovulation predictor kits detecting the LH surge are the most accessible accurate method. Basal body temperature confirms ovulation only after it has happened, and cycle-length estimates are the least reliable, particularly with irregular cycles.