When will implantation happen?
Enter the first day of your last period and your cycle length, or your ovulation day, to see when implantation is most likely and the full window in which it usually happens.
- Most likely implantation
- October 1, 2026 to October 3, 2026
Implantation most likely happens between October 1, 2026 and October 3, 2026.
- Most likely from
- October 1, 2026
- Most likely to
- October 3, 2026
- Possible from
- September 29, 2026
- Possible up to
- October 5, 2026
- Ovulation
- September 23, 2026
- Next period due
- October 7, 2026
Answer for the example date Wednesday, September 30, 2026. It changes to today's date when the page loads.
Most likely implantation: October 1, 2026 to October 3, 2026. Implantation most likely happens between October 1, 2026 and October 3, 2026.
When could implantation happen?
This calculator gives general information only. It is not medical advice and does not replace a doctor or other health care provider. Talk with a professional about your results. Terms of use
How to calculate
Estimates when implantation happens: 6 to 12 days after ovulation, most often 8 to 10, from the last period and cycle length or the ovulation date.
Example with the default inputs (What do you know? Last period, First day of your last period September 9, 2026, Cycle length (days) 28) on the example date Wednesday, September 30, 2026: Implantation most likely happens between October 1, 2026 and October 3, 2026.
Method: Ovulation = last period + cycle length − 14 days (or the day entered); implantation 6 to 12 days after ovulation, most likely 8 to 10 days after.
- Ovulation comes 14 days before the next period (ACOG average); real cycles vary.
- Implantation, seen as the first rise of hCG, happened 6 to 12 days after ovulation in pregnancies that lasted, and on day 8, 9 or 10 in 84% of them (Wilcox and others, 1999).
- These are estimates, not medical advice; spotting has many causes.
Worked examples
Each example is checked against the calculator on every build.
- What do you know? Last period, First day of your last period 2026-09-01, Cycle length (days) 28 gives Ovulation 2026-09-15, Most likely from 2026-09-23, Most likely to 2026-09-25, Most likely implantation September 23, 2026 to September 25, 2026, Possible from 2026-09-21, Possible up to 2026-09-27, Next period due 2026-09-29.Source: ACOG (ovulation 14 days before the next period); Wilcox 1999 (implantation 6 to 12 days after ovulation, 84% on days 8 to 10)
- What do you know? Last period, First day of your last period 2026-10-01, Cycle length (days) 32 gives Ovulation 2026-10-19, Most likely from 2026-10-27, Most likely to 2026-10-29, Next period due 2026-11-02.Source: Wilcox 1999
- What do you know? Ovulation day, Ovulation day 2026-12-28 gives Possible from 2027-01-03, Most likely from 2027-01-05, Most likely to 2027-01-07, Possible up to 2027-01-09.Source: Wilcox 1999 (6 to 12 days after ovulation, most often 8 to 10)
How it works
1. Ovulation. Either the ovulation day you enter, or
- ovulation = first day of the last period + (cycle length − 14) days,
for a cycle of 20 to 45 days. In a 28-day cycle that is 14 days after the first day of the period.
2. Implantation (Wilcox and others, 1999):
- possible window: ovulation + 6 days to ovulation + 12 days;
- most likely: ovulation + 8 days to ovulation + 10 days (84% of the pregnancies in the study).
3. Next period due = ovulation + 14 days.
The headline shows the most likely days as "September 23, 2026 to September 25, 2026". All dates are calendar dates with no time of day. The timeline shows ovulation, both implantation windows and the day the next period is due.
Assumptions
- The next period starts 14 days after ovulation (ACOG); real cycles vary, so the dates are estimates.
- The study timed implantation by the first rise of hCG in urine, in pregnancies conceived naturally.
- This calculator gives general information. It is not medical advice or a pregnancy test.
Worked examples by hand
Last period September 1, 2026, 28-day cycle. Ovulation = September 1 + 14 days = September 15. Possible implantation: September 15 + 6 = September 21 to September 15 + 12 = September 27. Most likely: September 23 to September 25. Next period due September 15 + 14 = September 29.
Last period October 1, 2026, 32-day cycle. Ovulation = October 1 + 18 days = October 19. Most likely implantation October 27 to October 29; next period due November 2.
Ovulation on December 28, 2026. Possible implantation from January 3 to January 9, 2027; most likely January 5 to January 7, 2027.
Other questions people ask
When does implantation happen?
In a study that measured hormones in daily urine samples (Wilcox and others, 1999), implantation in pregnancies that lasted happened 6 to 12 days after ovulation, and on day 8, 9 or 10 in 84% of them.
How is my ovulation day estimated?
Ovulation usually comes about 14 days before the next period. The calculator puts it at the first day of the last period + (cycle length − 14) days: 14 days after in a 28-day cycle, 18 days after in a 32-day cycle. If you track ovulation with tests or temperature, enter the ovulation day directly.
What is implantation bleeding?
Some people notice light spotting around the days implantation is expected. Spotting has many causes, so this calculator cannot tell you whether spotting is implantation; ask a health care provider about any bleeding that worries you.
When can I take a pregnancy test after implantation?
A home test detects hCG, which the body starts making at implantation. The level takes days to rise, so tests are most reliable from the day your period is due. See the pregnancy test calculator for the dates.
Does late implantation matter?
In the same study, early pregnancy loss was more common when implantation came later: 13% for implantation by day 9, rising to 26% on day 10, 52% on day 11 and 82% after day 11.
Can I use this after IVF?
Not directly. After an embryo transfer, the timing depends on the embryo’s age on transfer day. Ask your fertility clinic for the dates that fit your transfer.