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Ovulation Calculator

When is your next ovulation? This ovulation calculator gives you your fertile window, the exact ovulation date and when your next period is due – tailored to your individual cycle length.

✓ Vurdert av Julian Bronski · oppdatert juni 2026

Dine opplysninger

days
-3650+
days
2145+
days
1017+

Resultat

Ovulation (days from today)
Fertile window starts (days from today)
Fertile window ends (days from today)
Next period (days from today)
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Slik fungerer Ovulation Calculator

The calculation follows the standard scientific model: ovulation typically occurs cycle length − luteal phase days after the first day of your last period. The luteal phase (time between ovulation and the next period) is relatively constant for most women at 12–16 days, typically 14 days. The fertile window starts 5 days before ovulation (sperm survive up to 5 days) and ends 1 day after (egg viable for ~12–24 hours). Formulas: Ovulation = period + (cycle length − luteal phase) · Fertile window = ovulation − 5 to ovulation + 1 · Next period = period + cycle length.

Ofte stilte spørsmål

How accurate is the ovulation calculation?
The calendar method is an estimate based on average cycle patterns. It works well for regular cycles, but stress, illness or hormonal fluctuations can shift ovulation. For family planning or reliable contraception, combine it with basal body temperature tracking or LH ovulation test strips.
What is the luteal phase and why does it matter?
The luteal phase is the time between ovulation and the start of your next period. It is relatively constant at 12–16 days (default: 14 days). A luteal phase shorter than 10 days (luteal phase defect) can make implantation of a fertilised egg more difficult – consult a doctor if this applies to you.
Can I use this calculator instead of contraception?
No. This ovulation calculator is an information tool, not a contraceptive. The calendar method alone has a Pearl Index of around 9–25 (meaning 9–25 unintended pregnancies per 100 women per year with typical use). For reliable contraception, you need a medically supervised method.
Ikke finansiell eller medisinsk rådgivning. Uten garanti.

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