Our free ovulation calculator predicts your most fertile days from the first day of your last period and your average cycle length. In one click you see your estimated ovulation date, your fertile window, the date your next period is expected and the earliest day a home pregnancy test is likely to give a reliable result.

Use the ovulation calculator if you are trying to conceive, want to understand your cycle better or simply want to know when your next period is due. Your dates stay on your device and are never stored.

What Is Ovulation?

Ovulation is the moment an ovary releases a mature egg, usually once per menstrual cycle. The egg survives for about 12 to 24 hours, while sperm can survive in the body for up to 5 days. That is why the days leading up to ovulation are the most fertile. You can read more about ovulation and the menstrual cycle.

How to Use the Ovulation Calculator

Follow these four quick steps:

Step 1: Enter the First Day of Your Last Period

Choose the date your last period started from the calendar, for example 1 October 2026.

Step 2: Select Your Average Cycle Length

Pick the number of days from the start of one period to the start of the next. If you are unsure, use 28 Days (Standard). For the best results, average your last three to six cycles.

Step 3: Click Find Fertile Days

Press Find Fertile Days. The ovulation calculator works out your cycle dates instantly.

Step 4: Read Your Ovulation Date and Fertile Window

You will see your estimated ovulation date, your fertile window, your next expected period and an approximate pregnancy test date.

Ovulation Calculation Example

1. Last period started: 1 October 2026, cycle length 28 days.
2. Next period: 1 October + 28 days = 29 October 2026.
3. Ovulation: 29 October − 14 days = 15 October 2026.
4. Fertile window: 10 October to 15 October 2026.
5. Pregnancy test: from the day your period is due, 29 October.

Ovulation Dates by Cycle Length

For a last period starting on 1 October 2026:

Signs of Ovulation

• Cervical mucus changes: it becomes clear, slippery and stretchy, like raw egg white.
• Basal body temperature: a small rise of about 0.2 to 0.5°C after ovulation.
• Positive ovulation test: home LH tests detect the hormone surge 24 to 36 hours before ovulation.
• Mild pelvic pain: some people feel a twinge on one side, known as mittelschmerz.

How Accurate Is an Ovulation Calculator?

An ovulation calculator works best for regular cycles. Ovulation does not always happen exactly 14 days before a period, and stress, illness, travel or irregular cycles can shift it. For a more precise picture, combine the ovulation calculator with ovulation test strips or temperature tracking, and speak to a doctor if your cycles are very irregular or you have been trying to conceive for a long time.

Tips When Trying to Conceive

• Focus on the fertile window: the 2 to 3 days before ovulation are often the most fertile.
• Track several cycles: enter an average cycle length for a better estimate.
• Healthy habits help: balanced meals, regular sleep and not smoking support fertility.
• Already pregnant? Use our Due Date Calculator to estimate your due date.

Who Uses an Ovulation Calculator?

Couples trying for a baby use an ovulation calculator to plan intercourse on the most fertile days. Others use an ovulation calculator to learn their cycle pattern or to predict their next period. Because this ovulation calculator updates instantly, you can check a new cycle every month in seconds.

Frequently Asked Questions