Period & Ovulation Tracker
Enter your last period start date and average cycle length to see your predicted next period, fertile window, ovulation day, and where you are in your cycle right now — no app, no account, no data stored anywhere.
Your cycle info Free
Your predictions
Cycle overview
The white marker shows today's position in your cycle.
Next 6 cycles
| Cycle | Period starts | Fertile window | Ovulation (est.) |
|---|
Predictions assume your cycle stays consistent at the length entered above. The more irregular your cycles, the less reliable predictions further out become — treat cycles 3–6 as rough estimates, not certainties.
Quick answers
How does this calculate ovulation?
It uses the standard model: ovulation typically happens about 14 days before your next period starts (the luteal phase — the time between ovulation and your period — is usually a fairly consistent 12–14 days, even when the first half of your cycle varies). So ovulation day = cycle length − 14.
What is the "fertile window"?
The 5–6 days each cycle when pregnancy is possible: the 5 days before ovulation (sperm can survive that long) plus ovulation day itself (the egg survives about 24 hours after release). It's the same window methods like Flo and Clue use.
My cycles are irregular — is this still accurate?
Less so. This tool assumes a consistent cycle length, so the more your cycles vary month to month, the less reliable the prediction — especially for ovulation timing and cycles further in the future. If you track your actual cycle lengths over a few months, use the average, and treat the fertile window as a wider "roughly this week" estimate rather than exact days.
Why isn't my data saved anywhere?
This tool runs entirely in your browser — nothing you enter is sent to a server, stored in an account, or tracked. Close the tab and it's gone. If you want a running history across cycles, a dedicated app (with an account) will do that; this tool is built for a quick, private, no-signup check.