Ovulation Calculator
Estimate your likely ovulation day and fertile window from your last period and cycle length. Runs entirely in your browser.
⚠️ IMPORTANT: This is a rough estimate based on a calendar formula, NOT medical advice, and NOT a reliable method of contraception or of achieving pregnancy. Real cycles vary. For family planning or medical concerns, consult a doctor. Your inputs never leave your device.
Estimate your likely ovulation day and fertile window from your last period and cycle length. A calendar-based estimate for general awareness.
How to use
- Pick the first day of your last period.
- Enter your average cycle length.
- Calculate to see the estimated ovulation day and fertile window.
Frequently asked questions
When does ovulation usually happen?
Ovulation typically occurs about 14 days before the next period. This tool estimates it from your cycle length, along with a fertile window of roughly the five days before to one day after.
Can I use this for contraception?
No. This is a rough calendar estimate and is NOT a reliable method of contraception or of achieving pregnancy. Real cycles vary. For family planning, consult a doctor.
Is this medical advice?
No, it's for general awareness only. Speak to a healthcare professional for anything related to fertility or family planning.