Implantation calculator: when does implantation happen?
If you conceived, implantation would likely fall between Fri, Oct 16 and Thu, Oct 22
Implantation usually happens 6 to 12 days after ovulation (estimated Sat, Oct 10). Light spotting around then can be implantation bleeding, but many people never notice any.
🔒 Calculated in your browser. Nothing you type is sent or stored. Estimates only: cycles vary.
Implantation usually happens 6 to 12 days after ovulation, most often on day 8, 9 or 10. The calculator estimates ovulation as 14 days before your next expected period, then shows the 6 to 12 day window after it. A pregnancy test can only turn positive after implantation, so the most reliable day to test is still the day your period is due.
How the implantation calculator works
Enter the first day of your last period and your usual cycle length. The calculator works out when your next period is due, counts back 14 days to estimate ovulation, then shows the window 6 to 12 days after ovulation when a fertilized egg would most likely implant.
If you ovulated earlier or later than average, the window moves with it. LH tests or temperature tracking give a more precise ovulation date. Everything stays in your browser.
What happens at implantation
After an egg is fertilized in the fallopian tube, it travels to the uterus over several days while dividing into a ball of cells called a blastocyst. It then attaches to and burrows into the lining of the uterus. Only after this does the body start making hCG, the hormone pregnancy tests detect.
A classic study that tracked hormones daily in 221 women found that among pregnancies that continued, hCG first appeared 6 to 12 days after ovulation, and in 84% it was on day 8, 9 or 10. Later implantation was linked with a higher chance of early loss.
| Days after ovulation | What's going on |
|---|---|
| 0 to 1 | Ovulation; fertilization, if it happens, within about a day |
| 2 to 5 | The embryo travels down the tube and grows |
| 6 to 12 | Implantation window, most often days 8 to 10 |
| 10 to 14 | hCG rising; a sensitive test may turn positive |
| About 14 | Period due: the most reliable day to test |
Implantation bleeding: what it looks like
Some people notice light spotting around the time of implantation, though many never do. According to Cleveland Clinic it's usually pink or brown, much lighter than a period, lasts from a few hours to about two days, and may come with mild cramps. Because it often lands close to when your period is due, it's easy to confuse with an early, light period.
- Implantation bleeding: light spotting, pink or brown, no clots, doesn't build up, a day or two at most.
- A period: usually starts light then gets heavier, red, lasts several days, may include clots.
More side by side in implantation bleeding vs period and what implantation bleeding looks like. The two-week wait can also bring PMS-like feelings, because progesterone is high whether or not you're pregnant.
When to talk to a doctor
Get urgent help if you have a positive pregnancy test with heavy bleeding, one-sided belly pain, shoulder-tip pain or feeling faint, which can be signs of an ectopic pregnancy. See a doctor about any bleeding between periods that keeps happening, or bleeding after sex.
Frequently asked questions
When does implantation happen?
Usually 6 to 12 days after ovulation, most often 8 to 10 days after. In a 28-day cycle, that's around days 22 to 24.
Can I feel implantation?
Some people report mild cramps or spotting, but most people feel nothing. There's no reliable physical sign.
How soon after implantation can I test?
hCG needs a few days to build up. Testing on the day your period is due gives the most reliable result. Use the pregnancy test calculator.
Is implantation bleeding common?
Some light bleeding in early pregnancy is fairly common, but many people have none at all. Its absence doesn't mean anything.
Sources
- Wilcox AJ et al. Time of implantation of the conceptus and loss of pregnancy. NEJM (1999)
- Cleveland Clinic: Implantation bleeding
- NHS: Doing a pregnancy test
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
Keep reading
When to take a pregnancy test: find your most accurate dayWhen to take a pregnancy test: enter your last period and cycle length to see the earliest testing day and the day a result is most reliable.Implantation bleeding or period? How to tellImplantation bleeding vs period: color, flow, timing and how long each lasts. Spot the difference and learn when a pregnancy test will be accurate.What does implantation bleeding look like?What does implantation bleeding look like? Light pink or brown spotting, no clots, lasting hours to 2 days. How it differs from a period and when to test.
Spotting before your period: what's normal and why it happensSpotting before period starts is common. Why light pink or brown spotting shows up in the days before your period, what's normal, and the signs to check.
Ovulation calculator: when do I ovulate?Free ovulation calculator: enter your last period and cycle length to see your likely ovulation day for the next 4 cycles. Private, instant, estimates only.