Period Calculator

Predict your next period dates and ovulation window based on your cycle history.

First Day of Last Period (day)

Month

Year

Average Cycle Length (days)

Period Length (days)

Use Cases

Track menstrual cycle regularity
Plan for upcoming periods
Understand cycle patterns

Frequently Asked Questions

How accurate is period prediction?

Accuracy depends on cycle regularity. Irregular cycles make prediction less reliable.

What is a normal cycle length?

Cycle lengths of 21-35 days are considered normal. 28 days is the average.

What should I do if my period prediction is consistently wrong each month?

Track your cycle for 3-6 months to find your average cycle length. Irregular cycles over 35 or under 21 days may warrant a consultation with a healthcare provider.

How do hormonal contraceptives affect period prediction accuracy and cycle tracking?

Hormonal contraceptives like birth control pills create a controlled cycle, making period prediction very accurate since the timing is regulated by the medication rather than natural cycles.

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Disclaimer:

This period/ovulation calculator estimates dates based on the information you provide. It does not guarantee pregnancy, fertility, ovulation timing, or menstrual cycle accuracy and should not be used as birth control.