Ovulation Calculator
Estimate your ovulation date, fertile window, and next period from your last period, cycle length, and luteal phase. Free and instant.
Independently verified for accuracy
Calculator by Toolsloft ↗- Ovulation date
- 2026-06-15
- Fertile window start
- 2026-06-10
- Fertile window end
- 2026-06-16
- Next period date
- 2026-06-29
Estimate your ovulation date, your fertile window, and the start of your next period from the first day of your last period, your typical cycle length, and your luteal phase length. Useful for planning around the days when conception is most likely.
How this is calculated
Ovulation is estimated as the cycle length minus the luteal phase, counted in days after the first day of the last period. The fertile window spans the 5 days before ovulation to 1 day after it, and the next period is the last period plus one cycle length. This is an informational estimate, not medical advice; cycles vary, so consult a clinician for fertility decisions.
How to use
- Enter the first day of your last period.
- Enter your average cycle length and luteal phase in days.
- Read your estimated ovulation date, fertile window, and next period date.
Examples
- Last period 2026-06-01, 28-day cycle, 14-day luteal:
Ovulation 2026-06-15, fertile 2026-06-10 to 2026-06-16 - Last period 2026-06-10, 30-day cycle, 14-day luteal:
Ovulation 2026-06-26, fertile 2026-06-21 to 2026-06-27
FAQ
- How is the ovulation date estimated?
- Ovulation is estimated by subtracting your luteal phase length from your cycle length, then counting that many days after the first day of your last period.
- What is the fertile window?
- The fertile window here is the 5 days before ovulation through 1 day after it, the span when conception is most likely.
- How accurate is this estimate?
- It assumes a regular cycle and a fixed luteal phase. Real cycles vary month to month, so treat the result as a planning estimate rather than a precise prediction.