DPO Calculator (Days Past Ovulation)
Count how many days past ovulation (DPO) you are on any date, with your implantation window, the earliest day a sensitive pregnancy test may turn positive and when your period is due.
How it works
DPO = date to check − ovulation date (days) · Implantation ≈ 6–12 DPO · Expected period = ovulation + luteal phase · Gestational age = DPO + 14 days
Days past ovulation is how fertility trackers count the two-week wait. In the landmark study by Wilcox et al. (1999), implantation happened 6 to 12 days after ovulation, most often on days 8–10; hCG then enters the blood and, a few days later, the urine. Very sensitive tests may detect it from about 10 DPO, but many pregnancies are not positive until the day the period is due (usually 12–14 DPO), so a negative result before then is not final. Pregnancy weeks are counted from the last period, about 14 days before ovulation.
Worked example
Ovulation on October 1, 2026, checked on October 11, 2026: 11 − 1 = 10 days, so you are 10 DPO — inside the implantation window (October 7 – October 13). With a 14-day luteal phase your period is expected on October 15, 2026, and if you conceived you would be 3 weeks 3 days pregnant.
Sources: Wilcox AJ, Baird DD, Weinberg CR (1999) Time of implantation of the conceptus and loss of pregnancy. N Engl J Med 340:1796–1799 · Cole LA et al. (2004) Accuracy of home pregnancy tests at the time of missed menses. Am J Obstet Gynecol 190:100–105
Frequently asked questions
How many DPO can you get a positive pregnancy test?
Some very sensitive tests are positive from about 10 DPO, but only a minority of pregnancies show by then. By 12–14 DPO — around the missed period — most home tests are reliable. If negative and your period still has not come, retest 2–3 days later.
When does implantation happen?
Between 6 and 12 days after ovulation, most often 8–10 DPO. Some people notice light spotting (implantation bleeding) around then, but many notice nothing.
How do I know my ovulation date?
A positive LH ovulation test usually means ovulation within 24–36 hours, so take the following day. A sustained rise in basal body temperature confirms ovulation happened the day before the rise. Without either, assume ovulation about 14 days before your next period.
Are pregnancy symptoms at 5 DPO real?
Before implantation there is no hCG, so early symptoms are caused by progesterone, which rises after ovulation whether or not you conceive. They feel the same as premenstrual symptoms.
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This calculator is for education only and does not replace your midwife, obstetrician or doctor. Contact your care team straight away about bleeding, fluid leaking, reduced baby movements, severe pain or anything that worries you.