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🩸 Free Period Calculator

Predict your next period, ovulation, and fertile window.

What is this tool?

Our free period calculator helps track and predict menstrual cycles. Enter your last period date and average cycle length to get estimated dates for your next period, ovulation, and fertile window.

How it works

The calculator uses your average cycle length to predict future periods. Ovulation is estimated as approximately 14 days before your next period. The fertile window includes the 5 days before and the day of ovulation.

How to use

  1. Enter the start date of your last period.
  2. Set your average cycle length (typically 21-35 days).
  3. Enter your average period length.
  4. Click Calculate to see predictions.

Reference Table

Cycle LengthTypical Ovulation DayCommon
28 daysDay 14Most common
30 daysDay 16Common
35 daysDay 21Less common

Frequently Asked Questions

How accurate is this calculator?

This provides estimates based on averages. Individual cycles vary. For accurate tracking, monitor your cycle over several months.

What is a normal cycle length?

Normal cycle length ranges from 21 to 35 days. Variations of a few days are common.

Tips & Advice

Track your cycle for 3-6 months to identify your personal pattern. Stress, illness, and travel can affect cycle length. This calculator is for informational purposes only.

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