Period Calculator - calculatorsee.com


Period Calculator

Forecast future menstrual cycle dates, track period duration, and predict your next 3 menstrual periods.

Calculator Inputs

Date when bleeding began.
days
Number of days between period starts.
days
Days of menstrual bleeding.

Calculated Results

Next Period Expected
September 12, 2026
Estimated Ovulation Day August 29, 2026
Next Fertile Window August 25 - August 30, 2026
Current Cycle Phase Luteal Phase
Values calculate live as you adjust inputs.

About Period Calculator

Tracks menstrual regularity and projects future period start dates, fertile windows, and follicular/luteal hormonal phases.

What is Period Calculator?

Tracks menstrual regularity and projects future period start dates, fertile windows, and follicular/luteal hormonal phases.

How to Use This Calculator

  1. Select the first date of your last period.
  2. Enter your average cycle length and bleeding duration.
  3. Review expected upcoming period dates and ovulation window.

The Mathematical Formula & Variables

Next Period Date = Last Period Date + Cycle Length in days

Step-by-Step Worked Example

Scenario: Last period began August 15 with 28-day cycles.

  1. August 15 + 28 days = September 12, 2026.
  2. Ovulation occurs 14 days prior = August 29, 2026.

Result: September 12, 2026

Frequently Asked Questions

What is a normal menstrual cycle length?

A normal menstrual cycle ranges from 21 to 35 days in adult women, with 28 days being the statistical average.