Quick answer: With a period starting on 6 November 2026, a 28-day cycle and a 14-day luteal phase, ovulation is likely on 20 November 2026 (cycle day 15), with fertile days from 15 to 20 November.
How it's calculated
The time from ovulation to the next period, the luteal phase, is fairly steady at about 14 days (usually 12 to 16), while the time before ovulation varies. So ovulation is counted back from the next period: ovulation = period start + cycle length − luteal phase. If you know your luteal phase from ovulation tests or temperature charts, enter it.
The fertile window is the five days before ovulation plus ovulation day, the six days in which intercourse can lead to pregnancy (Wilcox et al., 1995). Each later cycle is the same pattern moved on by one cycle length. Some calculators show ovulation as a range of about two days either side of this day, and extend the fertile window to match.
These are predictions for regular cycles. Stress, illness, travel and breastfeeding can delay ovulation, and conditions such as polycystic ovary syndrome make it irregular. LH ovulation tests, cervical mucus and basal body temperature confirm the day in each cycle.
Worked examples
- Period 6 November 2026, 28-day cycle, luteal 14: 6 Nov + 28 − 14 = 20 November 2026
- Same start, 35-day cycle: 6 Nov + 35 − 14 = 27 November 2026
Frequently asked questions
Is ovulation always on day 14?
No. Ovulation around day 14 or 15 is typical only of a 28-day cycle. In a 35-day cycle ovulation is usually around day 22, and in a 24-day cycle around day 11.
What is the luteal phase?
The days from ovulation to the start of the next period. It is usually 12 to 16 days and changes little from cycle to cycle, which is why ovulation is counted back from the next period.
Can I use this to avoid pregnancy?
Calendar predictions alone are not a reliable form of contraception, because ovulation can shift without warning. Fertility-awareness methods combine several daily signs and are best learned with a health professional.
What are the signs of ovulation?
Clear, stretchy cervical mucus, a small rise in body temperature after ovulation and sometimes mild one-sided pain. Ovulation test strips detect the hormone surge a day or so before.
Can I have a period without ovulating?
Yes. Bleeding can happen in a cycle with no ovulation, especially in the teens, near menopause or with some hormone conditions. A calculator can't detect this.
How do I find my luteal phase length?
Track ovulation with test strips or body temperature, then count the days from ovulation to your next period. If you don't know it, leave it at 14 days.