Ovulation Calculator
Estimate your fertile window.
Mon, Jun 8, 2026
Fertile window: Wed, Jun 3, 2026 to Tue, Jun 9, 2026
| Event | Date |
|---|---|
| Last period started | Mon, May 25, 2026 |
| Fertile window starts | Wed, Jun 3, 2026 |
| Ovulation day | Mon, Jun 8, 2026 |
| Fertile window ends | Tue, Jun 9, 2026 |
| Next period due | Mon, Jun 22, 2026 |
Fertile days at a glance
Wed
Jun 3
Thu
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Fri
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Sat
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Mon
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Jun 9
Uses the standard 14-day luteal phase rule: ovulation = cycle length minus 14, counting from the first day of your last period. Sperm survive about five days, so the fertile window starts five days before ovulation. Cycles vary, so this is an estimate, not a guarantee.
About
Ovulation usually happens 14 days before your next period, not 14 days after the last one. The fertile window is the 5 days before ovulation plus the day of. This calculator uses your cycle length to estimate.
How to use
- Enter the first day of your last period.
- Enter your average cycle length.
- See the predicted ovulation date and fertile window.
FAQ
How accurate is this?+
Calendar-based prediction is rough. Cycle length varies. For more precision, track basal body temperature or use ovulation predictor kits (LH strips).
Is the math reliable for irregular cycles?+
Less so. If your cycle varies by more than a few days, the predicted window can be off by a week. Tracking sticks works better.