Health

Instant, private, and free

Ovulation Calculator.

Track your fertile window and next period

On-device calculationNo signup
01

Set your values

Results update as you type.

Cycle Information

The number of days from the first day of one period to the first day of the next. Most cycles run 21-35 days.

These dates are estimates based on a regular cycle. Actual ovulation varies from cycle to cycle and can shift with stress, illness, or medication. This tool is not a form of contraception or medical advice.

Estimated Ovulation Day

October 11, 2026
Peak Fertility Window
Fertile Window Starts: October 6, 2026

Fertile Window Starts

October 6, 2026
Fertile Window Ends: October 12, 2026

Fertile Window Ends

October 12, 2026
Next Period Starts: October 25, 2026

Next Period Starts

October 25, 2026
Due Date If Conceived: July 4, 2027

Due Date If Conceived

July 4, 2027

Planning Tip

The days leading up to ovulation are generally the most fertile. Tracking a few cycles gives a more reliable pattern than a single estimate.

FAQs

When does ovulation typically happen?

Ovulation generally occurs about 14 days before your next period starts. In a standard 28-day cycle, this is usually on day 14.

How long is the fertile window?

The fertile window lasts about 6 days—the 5 days leading up to ovulation and the day of ovulation itself. Sperm can live inside the female body for up to 5 days.

How accurate are ovulation calculators?

They provide a good estimate based on averages, but individual cycles can vary due to stress, illness, or hormonal changes. For more accuracy, consider using ovulation predictor kits (OPKs) or tracking basal body temperature.

Cite this calculator

Canonical URL: https://mathify.one/de/health/ovulation

Cite as: Mathify. (2026). Eisprungrechner. https://mathify.one/de/health/ovulation

Use Cases

Plan for Conception

Identify your most fertile days to time intercourse for the best chance of getting pregnant.

Example: If your cycle is 28 days, your fertile window might be days 10-15.

Understand Your Cycle

Learn when ovulation likely occurs to better understand your body's patterns and plan accordingly.

Example: Track your cycle length to see how your fertile days shift.

Frequently Asked Questions

How does the Ovulation Calculator estimate my fertile days?
Based on your menstrual cycle length and the first day of your last period, the calculator estimates your ovulation date (typically 14 days before your next period) and highlights your fertile window, which includes the days leading up to and including ovulation.
What is the fertile window and why is it important?
The fertile window is the days when you are most likely to conceive, usually about 6 days ending on ovulation day. Sperm can survive up to 5 days, so having intercourse during this window increases your chances of pregnancy.
Is this calculator a substitute for medical advice?
No, this calculator provides an estimate based on average cycle data. For personalized guidance or if you have irregular cycles, consult a healthcare provider.

Tips & Common Mistakes

Tips

  • Track your cycle length for at least 3 months to get a more accurate average.
  • Use the calculator in conjunction with other fertility signs like cervical mucus or basal body temperature.
  • Remember that sperm can survive up to 5 days, so start trying a few days before ovulation.
  • For irregular cycles, the estimate may be less accurate; consider consulting a specialist.

Common Mistakes to Avoid

  • Assuming every cycle is exactly 28 days – cycle lengths vary, so use your own average.
  • Only focusing on the ovulation day itself, but the fertile window includes several days before.
  • Not updating the calculator with your actual cycle length each month.

Last updated: August 13, 2026