Ovulation calculator for a 28-day cycle
Ovulation ~Friday, October 30 · fertile Sun, Oct 25 – Sat, Oct 31
Ovulation ~Friday, November 27 · fertile Sun, Nov 22 – Sat, Nov 28
Ovulation ~Friday, December 25 · fertile Sun, Dec 20 – Sat, Dec 26
🔒 Calculated in your browser. Nothing you type is sent or stored. Estimates only: bodies vary.
With a 28-day cycle, you most likely ovulate around cycle day 14 (day 1 is the first day of your period). Your fertile window is roughly days 9 to 15, and your best chance of conceiving is from day 12 to day 14. Enter your last period above to turn that into dates.
When do you ovulate with a 28-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 28-day cycle you count back 14 days from day 29 (the first day of your next period) and land on day 14.
| Cycle day | What usually happens in a 28-day cycle |
|---|---|
| 1 to 5 | Your period (most people bleed 3 to 7 days) |
| 6 to 8 | Follicular phase: estrogen rises, energy and mood usually lift |
| 9 to 13 | Fertile window opens: sperm can survive up to 5 days |
| 14 | Estimated ovulation, the most fertile day along with the 2 days before |
| 15 to 28 | Luteal phase: progesterone rises; PMS often shows up in the last week |
Your fertile window with a 28-day cycle
An egg lives for about 12 to 24 hours after ovulation, but sperm can survive up to five days. That makes days 9 to 15 your fertile window, with the highest chances on days 12, 13 and 14. 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 28-day cycle, start daily ovulation (LH) tests on cycle day 12, 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 28-day cycle normal?
A 28-day cycle is right in the middle of the normal range (21 to 35 days). Large app studies put the average cycle at about 29 days, so the famous 28 days is close to typical, not a rule.
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.
28-day cycle compared with other cycle lengths
| Cycle length | Likely ovulation day | Fertile window |
|---|---|---|
| 24 days | day 10 | days 5 to 11 |
| 26 days | day 12 | days 7 to 13 |
| 28 days (yours) | day 14 | days 9 to 15 |
| 30 days | day 16 | days 11 to 17 |
| 32 days | day 18 | days 13 to 19 |
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 28-day cycle?
Most likely around day 14, 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 28-day cycle?
Have sex every 1 to 2 days from about day 9 to day 15, with the most fertile days being 12 to 14.
Can I get pregnant right after my period with a 28-day cycle?
It's less likely but possible: your fertile window usually opens around day 9, 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 28-day cycle?
From the day your period is due, day 29, 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 26-day cycleWith a 26-day cycle you usually ovulate around day 12, fertile days 7 to 13. See your exact dates for the next three cycles, free.Ovulation calculator for a 27-day cycleWith a 27-day cycle you usually ovulate around day 13, fertile days 8 to 14. 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.