My cycles are irregular. What should I do?

Enter your average cycle length over the last six months. If cycles differ by more than 7 to 9 days, the calculation is unreliable: ovulation tests and basal temperature are more useful.

Can you get pregnant during your period?

It is rare but possible with short cycles, because sperm survive several days and ovulation can come early.

What are the signs of ovulation?

Abundant, clear, stretchy cervical mucus, sometimes a mild one-sided pain in the lower abdomen, a higher libido, then a rise in basal temperature the following day.

When should I see a doctor?

After 12 months of trying without pregnancy (6 months after 35), or earlier if your cycles are very irregular or absent.

Free

Ovulation calculator

Enter the first day of your last period and your usual cycle length to estimate your ovulation and your fertile window.

Free, no sign-up, nothing stored

First day of your last period

Cycle length (days)Period length (days)

Luteal phase (days, optional)

14 days by default; enter yours if you know it from temperature tracking.

Shortest cycle (optional)Longest cycle (optional)

Ovulation happens about 14 days before the next period, not 14 days after the last one: that is why your cycle length matters.

Enter a date to see your fertile days.

The four phases of the cycle

1Menstrual
Days 1 to 5. Oestrogen and progesterone at their lowest, the lining sheds. Energy is often low: rest, warmth, iron.
2Follicular
After the period until ovulation. Oestrogen rises, a follicle matures; energy, mood and skin improve.
3Ovulatory
The LH surge releases the egg. Clear, stretchy mucus, higher libido, sometimes a one-sided twinge.
4Luteal
After ovulation until the period. Progesterone rises, so does basal temperature; breast tenderness, appetite, lighter sleep towards the end.

Ovulation calculator

How it works

In a cycle, ovulation usually happens 12 to 16 days before the next period. The tool uses 14 days: with a 28-day cycle, ovulation is estimated on day 14; with a 32-day cycle, on day 18.
Sperm can survive up to 5 days in the uterus, the egg about 24 hours. The fertile window therefore covers the 5 days before ovulation and the day itself; the two days before ovulation are the most favourable.
This is an average. To refine it, you can watch your cervical mucus (clear and stretchy before ovulation), take your temperature on waking (it rises by 0.2 to 0.5 °C after ovulation) or use ovulation tests from a pharmacy, which detect the LH surge 24 to 36 hours before.
This tool is not a contraceptive method: intercourse outside the estimated window can still lead to pregnancy, especially with irregular cycles.

These tools give general information. They do not replace the advice of a doctor or a qualified professional.

Go furtherPregnancy & postpartum

Frequently asked questions

My cycles are irregular. What should I do?: Enter your average cycle length over the last six months. If cycles differ by more than 7 to 9 days, the calculation is unreliable: ovulation tests and basal temperature are more useful.
Can you get pregnant during your period?: It is rare but possible with short cycles, because sperm survive several days and ovulation can come early.
What are the signs of ovulation?: Abundant, clear, stretchy cervical mucus, sometimes a mild one-sided pain in the lower abdomen, a higher libido, then a rise in basal temperature the following day.
When should I see a doctor?: After 12 months of trying without pregnancy (6 months after 35), or earlier if your cycles are very irregular or absent.

How it works

Frequently asked questions

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