Health & WellbeingLive

Ovulation Calculator

Estimate your ovulation day and 6-day fertile window.

Short answer

Ovulation typically happens ~14 days before your next period. The fertile window covers the 5 days before ovulation and the day itself, since sperm survive up to 5 days.

Cycle

First day of last period (YYYY-MM-DD)

Average cycle length (days)

Fill in the fields above to see your result instantly.

How it works

Assumes a fixed 14-day luteal phase (most reliable phase). Ovulation = LMP + cycle length − 14. Fertile window = 5 days before ovulation through ovulation day.

Worked example

LMP 1 Apr, 28-day cycle: ovulation ~ 15 Apr; fertile window 10–15 Apr; next period ~ 29 Apr.

Who should use this

•People trying to conceive
•Anyone tracking cycles for awareness

Common mistakes

×Using as contraception — too unreliable on its own
×Assuming 28-day cycle when yours varies

Frequently asked questions

Is this safe to use as contraception?▾

No. Even careful fertility awareness methods have ~5-25% failure rates.

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