Ovulation calculator for a 39-day cycle
Ovulation ~Tuesday, November 10 · fertile Thu, Nov 5 – Wed, Nov 11
Ovulation ~Saturday, December 19 · fertile Mon, Dec 14 – Sun, Dec 20
Ovulation ~Wednesday, January 27 · fertile Fri, Jan 22 – Thu, Jan 28
🔒 Calculated in your browser. Nothing you type is sent or stored. Estimates only: bodies vary.
With a 39-day cycle, you most likely ovulate around cycle day 25 (day 1 is the first day of your period). Your fertile window is roughly days 20 to 26, and your best chance of conceiving is from day 23 to day 25. Enter your last period above to turn that into dates.
When do you ovulate with a 39-day cycle?
Ovulation usually happens about 14 days before your next period, not 14 days after the last one. The part of the cycle after ovulation, the luteal phase, is fairly steady at 12 to 14 days for most people, while the part before it stretches or shrinks. So with a 39-day cycle you count back 14 days from day 40 (the first day of your next period) and land on day 25.
| Cycle day | What usually happens in a 39-day cycle |
|---|---|
| 1 to 5 | Your period (most people bleed 3 to 7 days) |
| 6 to 19 | Follicular phase: estrogen rises, energy and mood usually lift |
| 20 to 24 | Fertile window opens: sperm can survive up to 5 days |
| 25 | Estimated ovulation, the most fertile day along with the 2 days before |
| 26 to 39 | Luteal phase: progesterone rises; PMS often shows up in the last week |
Your fertile window with a 39-day cycle
An egg lives for about 12 to 24 hours after ovulation, but sperm can survive up to five days. That makes days 20 to 26 your fertile window, with the highest chances on days 23, 24 and 25. In the classic study of couples trying to conceive, sex on the two days before ovulation and on ovulation day itself carried the highest chance, about 27 to 33% per cycle.
With a 39-day cycle, start daily ovulation (LH) tests on cycle day 23, about 17 days before your next period is due, and keep going until you get a positive. Ovulation usually follows 24 to 36 hours later. See our ovulation test calculator.
Is a 39-day cycle normal?
A 39-day cycle is longer than the usual 21 to 35 days. It can be normal for you, especially in your teens or in perimenopause, but regularly longer cycles can be a sign of irregular ovulation (for example with PCOS or thyroid changes). It's worth tracking a few months and talking to a doctor.
Cycles also vary from month to month. If yours swing by several days, use the dates as a starting point and check signs of ovulation such as stretchy, clear discharge or a positive LH test. Our ovulation calculator for irregular periods works from your last few cycles instead of a single number.
39-day cycle compared with other cycle lengths
| Cycle length | Likely ovulation day | Fertile window |
|---|---|---|
| 35 days | day 21 | days 16 to 22 |
| 37 days | day 23 | days 18 to 24 |
| 39 days (yours) | day 25 | days 20 to 26 |
| 41 days | day 27 | days 22 to 28 |
| 43 days | day 29 | days 24 to 30 |
Calendar dates are estimates and are not a method of contraception. See a doctor if your cycles are often shorter than 21 or longer than 35 days, if periods stop for 3 months, or if you've been trying to conceive for 12 months (6 months if you're 35 or older).
Frequently asked questions
What day do I ovulate on a 39-day cycle?
Most likely around day 25, counting the first day of your period as day 1. It can move a day or two either way from cycle to cycle.
When is the best time to try to conceive with a 39-day cycle?
Have sex every 1 to 2 days from about day 20 to day 26, with the most fertile days being 23 to 25.
Can I get pregnant right after my period with a 39-day cycle?
It's less likely but possible: your fertile window usually opens around day 20, and sperm can survive up to five days, so an early ovulation or a long period could overlap.
When should I take a pregnancy test with a 39-day cycle?
From the day your period is due, day 40, for an accurate result. Use our pregnancy test calculator for the exact date.
Sources
- Wilcox AJ et al. Timing of sexual intercourse in relation to ovulation. NEJM (1995)
- Bull JR et al. Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles. npj Digital Medicine (2019)
- NHS: Periods and fertility in the menstrual cycle
- ACOG: Evaluating Infertility FAQ
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
Keep reading
Ovulation calculator for a 37-day cycleWith a 37-day cycle you usually ovulate around day 23, fertile days 18 to 24. See your exact dates for the next three cycles, free.Ovulation calculator for a 38-day cycleWith a 38-day cycle you usually ovulate around day 24, fertile days 19 to 25. See your exact dates for the next three cycles, free.
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.
Fertile window calculator: when am I most fertile?Free fertile window calculator: see the days each cycle when pregnancy is most likely, for your next 4 cycles. Private, estimates only, not contraception.How many days after your period do you ovulate?How many days after your period is ovulation? Often about 7 to 10 days after bleeding stops, but it depends on your cycle. A simple way to work it out.
Ovulation phase: signs, timing and feelingsThe ovulation phase explained: when you ovulate, how long it lasts, the signs and symptoms to look for, and why mood, energy and libido often peak.