Ovulation Calculator
Estimate your ovulation date and fertile window based on your last period and cycle length.
Cycle details
Not sure of your luteal phase length? 14 days is a typical default — most people don't know theirs exactly unless it's been measured.
Estimated fertile window
Sat, Jan 10, 2026 – Fri, Jan 16, 2026
Estimated ovulation date
Thu, Jan 15, 2026
Next period expected
Thu, Jan 29, 2026
Following cycles
- Thu, Feb 12, 2026
- Thu, Mar 12, 2026
This is a statistical estimate based on average cycle timing, not a measurement of your actual ovulation — actual timing varies cycle to cycle. It is not a reliable method of contraception. If you're tracking for conception or have fertility concerns, talk to a healthcare provider.
How this is calculated
Ovulation date = last period start + (cycle length − luteal phase length). Fertile window = 5 days before ovulation through 1 day after. Next period = last period start + cycle length.
Pricing is verified against provider pricing pages as of 2026-09-01. AI and cloud pricing changes frequently — confirm the current rate on the provider's own pricing page before budgeting.
Frequently asked questions
How is ovulation date estimated?
Ovulation is estimated to occur a fixed number of days (the luteal phase, typically ~14 days) before your next expected period — this offset is more consistent than the time from period start to ovulation, which varies with cycle length.
What is the fertile window?
The days in a cycle when conception is possible — sperm can survive in the reproductive tract for up to 5 days, and the egg is viable for about 24 hours after ovulation, giving a window of roughly 6 days ending the day after estimated ovulation.
How accurate is this estimate?
It's a statistical estimate based on average cycle patterns, not a measurement of your actual ovulation — actual timing varies cycle to cycle, especially with irregular cycles, stress, illness, or travel. Ovulation predictor kits or tracking basal body temperature give more direct signals.
Can I use this for contraception?
No — this calculator is not a reliable method of contraception. Cycle-based estimates can be wrong in either direction, and unprotected sex outside the calculated window can still result in pregnancy. Talk to a healthcare provider about reliable contraception options.