Period & Ovulation Calculator
Estimate your next period, ovulation day, and fertile window from your last cycle start date.
The day bleeding started, not when it ended. Use today's date if you're starting now.
Forecast for the next 6 cycles
- Cycle 1in 28dPeriod5 Jul 2026 – 9 Jul 2026Ovulation21 Jun 2026
- Cycle 2in 56dPeriod2 Aug 2026 – 6 Aug 2026Ovulation19 Jul 2026
- Cycle 3in 84dPeriod30 Aug 2026 – 3 Sep 2026Ovulation16 Aug 2026
- Cycle 4in 112dPeriod27 Sep 2026 – 1 Oct 2026Ovulation13 Sep 2026
- Cycle 5in 140dPeriod25 Oct 2026 – 29 Oct 2026Ovulation11 Oct 2026
- Cycle 6in 168dPeriod22 Nov 2026 – 26 Nov 2026Ovulation8 Nov 2026
How to use
- 1
Pick the date your last period started (the first day of bleeding, not the last).
- 2
Enter your average cycle length — count from one period start to the next, not the days you bleed.
- 3
Optional: your average period length and how many future cycles to forecast.
- 4
The result shows your next period date, fertile window, and ovulation day. The fertile window is the ~6-day span when pregnancy is possible.
Frequently asked questions
For people with regular cycles (length varies by less than ~5 days between months), it's accurate to within 1-2 days. For irregular cycles, it's a rough guide only. Ovulation prediction kits (OPKs) measuring luteinizing hormone, or basal body temperature tracking, are more precise — but for most purposes a calendar estimate is enough.
The standard 'luteal phase = 14 days' model: ovulation happens roughly 14 days before your next period. So if your cycle is 28 days, ovulation is day 14. If it's 32 days, ovulation is day 18. This is more accurate than 'day 14 of every cycle' because the luteal phase is much more consistent than the follicular phase.
The ~6-day span when intercourse can result in pregnancy: 5 days before ovulation + the day of ovulation + 1 day after. Sperm live up to 5 days inside the body, but the egg only lasts 12-24 hours after release. The day of ovulation and the day before are the highest-chance days.
No. Calendar-based methods alone are not reliable contraception (typical-use failure rate is ~24% per year per the CDC). For pregnancy prevention, use a medical method (IUD, hormonal, barrier) — and consult a doctor about what suits you. This calculator is for awareness, family planning, or to figure out when your next period is due.
Today's date is part of the calculation — 'days from today' updates as the calendar moves. Stored cycle dates don't change; only the 'X days from now' figures do.
The day before ovulation and the day of ovulation. Pregnancy rates peak at around 30% per cycle when intercourse happens on those days. The fertile window starts wider (5 days before) because sperm survive — but the peak is the day before ovulation.
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Source: ACOG (American College of Obstetricians and Gynecologists) — standard luteal-phase model · Last verified 2026-06. ACOG. This tool provides estimates only and is not legal, tax or financial advice. Always verify your specific situation with the relevant UAE authority or a licensed advisor before taking action.