Skip to main content

Ovulation Calculator

Find the days you are most likely to get pregnant. Enter the first day of your last period and your usual cycle length to see your fertile window, likely ovulation date and next period on a calendar.

  • Free, no sign-up
  • Nothing you enter is stored
  • Updated 30 Sept 2026

Find your fertile days

For people with fairly regular cycles.

21 days35 days

Days from the start of one period to the start of the next; 28 is typical

2 days10 days

Your fertile days will appear here

Enter the first day of your last period and your usual cycle length, then press Calculate.

What is ovulation?

Ovulation is when one of your ovaries releases an egg. The egg can be fertilised for about 12 to 24 hours. Sperm can survive in the body for up to five days, so you can get pregnant from sex in the days before ovulation as well as on the day itself.

How does the ovulation calculator work?

The second half of the cycle, from ovulation to the next period, usually lasts about 14 days. So the calculator counts back 14 days from your next expected period to estimate when you ovulate.

Likely ovulation date

First day of last period + (cycle length − 14 days)

For example, if your last period started on 1 Sept 2026 and your cycle is 28 days long, you would likely ovulate on 15 Sept 2026. Your fertile window would be 10 Sept to 15 Sept 2026, and your next period would be due on 29 Sept 2026.

What is the fertile window?

Your fertile window is the six days that end on the day you ovulate. Sex during these days gives the best chance of pregnancy, and the chance is highest in the two days before ovulation and on the day itself.

Cycle lengthLikely ovulationFertile window
26 daysDay 13Days 8 to 13
28 daysDay 15Days 10 to 15
30 daysDay 17Days 12 to 17
32 daysDay 19Days 14 to 19

Day 1 is the first day of your period.

Signs of ovulation

  • Cervical mucus becomes clear, slippery and stretchy, like raw egg white.
  • Your resting body temperature rises slightly, by about 0.3 to 0.5°C, after ovulation.
  • Some people feel a mild ache on one side of the lower belly.
  • Home ovulation test kits detect the hormone surge that comes one to two days before ovulation.

If your cycles are irregular

This calculator works best when your cycle is between 21 and 35 days and about the same length each month. If your cycle length changes by more than a week from month to month, the dates will be less reliable.

Stress, illness, travel, weight changes and conditions such as polycystic ovary syndrome (PCOS) or thyroid problems can all shift ovulation. Tracking signs of ovulation or using test kits gives a closer answer, and a doctor can help if your cycles are often irregular.

When to see a doctor

  • You are under 35 and have been trying to get pregnant for a year without success.
  • You are 35 or older and have been trying for six months.
  • Your periods are very irregular, very painful or have stopped.

Frequently asked questions

1.How accurate is an ovulation calculator?

It gives a good estimate if your cycles are regular, but ovulation can move by a few days from month to month. For more accuracy, combine it with signs such as cervical mucus changes or a home ovulation test.

2.How many days after my period do I ovulate?

Ovulation usually happens about 14 days before your next period. In a 28-day cycle that is around day 14 or 15, counting the first day of your period as day 1. In longer or shorter cycles it moves later or earlier.

3.Can I get pregnant outside the fertile window?

It is unlikely but possible, especially if your cycle is irregular or you ovulate earlier or later than usual. Sperm can live for up to five days, which widens the window.

4.Can I use this calculator to avoid pregnancy?

No. Ovulation dates are estimates and can change without warning, so this calculator is not a reliable form of birth control. Speak to a doctor about contraception.

5.When should I take a pregnancy test?

Most home pregnancy tests are accurate from the first day of a missed period. Testing earlier can give a false negative, so wait until your period is due.

6.Does the calculator store my dates?

No. The calculation runs in your browser, and the dates you enter are not sent to Policywings or saved.

Calculators

Popular calculators

Free tools to put real numbers on your money, health and family plans before you choose a policy. Pick one to get started.

View all health calculatorsView all financial calculators
Explore cover

Protect your health with the right cover

Good numbers lower many health risks, but they cannot rule them out. Compare plans that pay for hospital care and protect your family.

Need help with a claim?Our team stays with you from intimation to settlement.

Guides to read next

Plain-English guides from the Policywings desk on the same topic as this calculator.

All health insurance articles