Period & Ovulation Tracker

estimate your next period, ovulation day & fertile window

Privacy-first: your entries stay on your device only. No account, no cloud sync, no tracking.

Your cycle details

First day of last period

Average cycle length

Average period length

Your Cycle Estimate

Next period—

Estimated ovulation—

Fertile window—

Why track your cycle?

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Predict your cycle

Know when your next period will start so you're never caught off guard.

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Identify ovulation

Track your fertile window for family planning, in either direction.

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Understand patterns

Spot changes in cycle length over time that are worth discussing with a doctor.

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Complete privacy

Your dates stay on your device. No cloud storage, no data collection.

How it works

Enter the first day of your last period. That's the one date this calculator actually needs.
Set your average cycle and period length. 28-day cycles and 5-day periods are typical defaults, but adjust to match your own pattern if you know it.
We estimate your next period by adding your cycle length to your last period's start date.
We estimate ovulation as roughly 14 days before your next period, with a 6-day fertile window (5 days before ovulation through 1 day after) reflecting sperm and egg viability.
Your calendar shows the pattern projected across the next few cycles.

Important: Ovulation estimates aren't exact — actual timing can shift by several days each cycle. This isn't a method of birth control. If you have irregular cycles, very heavy bleeding, severe pain, or think you might be pregnant, talk to a clinician.