ovulation calculator
Find your fertile window and best days to conceive — covers 6 upcoming cycles — free, no sign-up.
This calculator provides estimates only and should not be used as contraception. Ovulation can shift due to stress, illness, travel, or hormonal changes. Consult your healthcare provider for fertility guidance.
The menstrual cycle
| Menstruation | Days 1–5 |
| Follicular | Days 1–13 |
| Fertile window | Days 10–15 |
| Ovulation | Day 14 (avg) |
| Luteal phase | Days 15–28 |
When is the fertile window?
The fertile window is the 6 days ending on ovulation day. Sperm can survive up to 5 days inside the body, so having sex in the days leading up to ovulation gives the best chance of conception.
Peak fertility days
The 2 days before ovulation and ovulation day itself are your most fertile days. Pregnancy is unlikely but not impossible outside this window.
FAQ
What is the luteal phase?
The luteal phase is the time between ovulation and your next period. It averages 14 days and is relatively consistent — adjusting this setting improves accuracy for irregular cycles.
Can stress delay ovulation?
Yes — stress, illness, travel, and significant weight changes can delay or suppress ovulation, making calculator predictions less accurate for that cycle.
How can I confirm ovulation?
LH surge ovulation test strips, basal body temperature tracking, and cervical mucus monitoring are the most reliable at-home methods to confirm ovulation.
Is my data stored?
No — everything runs in your browser. No dates or personal data are ever uploaded or stored.