Ovulation calendar calculator: your next 3 months at a glance
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.
This ovulation calendar calculator lays out your next three cycles. It adds your cycle length to the first day of your last period to find each next period, places ovulation about 14 days before it, and marks the fertile window: the five days before ovulation plus the day after. Each month shows as a calendar colored by phase.
How the ovulation calendar calculator works
- Enter the first day of your last period, your usual cycle length and how many days you usually bleed.
- The calculator works out your next period, then puts estimated ovulation 14 days before it. That gap (the luteal phase) stays fairly steady for most people, while the first half of the cycle varies.
- It marks your ovulation window: the five days before ovulation, ovulation day and the day after.
- It repeats this for three cycles and draws each as a small calendar.
Everything is calculated in your browser. Nothing you type is sent to us or saved anywhere.
How to read your ovulation calendar
Each cycle gets one line and one calendar. The line gives the estimated ovulation day and the fertile window dates. On the calendar, every day is colored by phase, the sun marks estimated ovulation, and today has an outline.
| Color on the calendar | Phase | What it means |
|---|---|---|
| Period | Menstrual | The days you're likely bleeding, based on your period length |
| Follicular | Follicular | After your period, before the fertile window. An egg is maturing |
| Fertile | Ovulatory | Your estimated ovulation window, with the sun on ovulation day |
| Luteal | Luteal | After ovulation until your next period. PMS often shows up here |
The ovulation window, cycle by cycle
The window moves with your cycle length. Here's where it usually falls, counting day 1 as the first day of bleeding:
| Cycle length | Estimated ovulation | Fertile window |
|---|---|---|
| 24 days | around day 10 | days 5 to 11 |
| 26 days | around day 12 | days 7 to 13 |
| 28 days | around day 14 | days 9 to 15 |
| 30 days | around day 16 | days 11 to 17 |
| 32 days | around day 18 | days 13 to 19 |
| 35 days | around day 21 | days 16 to 22 |
The most fertile days are the two days before ovulation and ovulation day itself. Our fertile window calculator explains the odds day by day.
Worked example
Your last period started on 2 January and your cycles are 30 days. The calendar shows:
- Cycle 1: ovulation around 18 January, fertile 13 to 19 January, next period 1 February.
- Cycle 2: ovulation around 17 February, fertile 12 to 18 February, next period 3 March.
- Cycle 3: ovulation around 19 March, fertile 14 to 20 March, next period 2 April.
How accurate is an ovulation calendar?
A calendar is a plan, not a measurement. Large app studies show that even people with regular cycles ovulate on different days from one month to the next, and the further ahead you look, the more the dates can drift. Use the calendar to know roughly when to pay attention, then confirm with your body:
- Ovulation (LH) tests show the hormone surge a day or so before ovulation. Our ovulation test calculator tells you when to start.
- Cervical mucus turns clear, slippery and stretchy, like raw egg white, near ovulation.
- Basal body temperature rises slightly after ovulation and stays up until your period.
- If your cycles vary by more than a week, try the ovulation calculator for irregular periods, which uses your own range.
Calendar dates are estimates and are not a reliable 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 a year (6 months if you're 35 or older).
Your calendar is a mood calendar too
The same phases that move ovulation also move how you feel. Many people find their month follows a rough rhythm:
Frequently asked questions
How do I calculate my ovulation window?
Find your next period date, count back 14 days for ovulation, then take the five days before it and the day after. That's your window.
Can I use an ovulation calendar if my periods are irregular?
You can, but the dates will be rough. With irregular cycles, ovulation tests and cervical mucus tell you much more than averages.
Why does my ovulation day change every month?
The first half of the cycle can stretch or shrink with stress, illness, travel or sleep, so ovulation moves. The time from ovulation to your period stays steadier.
Is an ovulation calendar the same as a fertility calendar?
Yes, people use both names. Both mark the days when pregnancy is possible, centered on estimated ovulation.
Sources
- NHS: Fertility in the menstrual cycle
- Bull JR et al. Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles. npj Digital Medicine (2019)
- Wilcox AJ et al. The timing of the fertile window in the menstrual cycle. BMJ (2000)
- Cleveland Clinic: Ovulation
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
Keep reading
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.
Period and ovulation calculator: both dates in one placeFree period and ovulation calculator: see your next 6 periods plus this cycle's ovulation day and fertile window on one calendar. Private, nothing is stored.The 4 phases of the menstrual cycle, in colorThe 4 phases of the menstrual cycle explained simply: what your hormones do in each, how long each lasts, and how mood and energy usually change.How long does ovulation last?How long does ovulation last? The egg is released in moments and lives 12 to 24 hours, but the fertile window lasts about 6 days. Here's how it all fits.