Cycle Length Calculator

Enter the start date of each period for the last 3–6 cycles

Cycle length is the number of days from the first day of one period to the day before the next period starts.

Cycle 1 Start Date

Cycle 2 Start Date

Cycle 3 Start Date

About Cycle Length Tracking

Understanding your menstrual cycle length is fundamental for reproductive health, fertility planning, and overall well-being. The average cycle length is typically between 21-35 days, with 28 days being the standard. However, individual variation is completely normal and healthy.

How the Cycle Length Calculator Works

Our calculator helps you determine your personalized average cycle length by analyzing the start dates of your recent periods:

Calculation Method

Enter the start date of each period for the last 3-6 cycles
We calculate each cycle length (start date to start date of next period)
We average all cycle lengths to determine your personalized cycle length
We provide predictions for your next period and ovulation

Example Calculation

Cycle 1: Jan 1 to Jan 28 = 28 days
Cycle 2: Jan 28 to Feb 26 = 29 days
Cycle 3: Feb 26 to Mar 27 = 30 days
Average: (28+29+30)/3 = 29 days

Benefits of Tracking Your Cycle Length

Regular cycle tracking provides valuable insights into your reproductive health:

Fertility Planning

Accurate ovulation prediction for conception timing
Better understanding of your fertile window
Improved success rates when trying to conceive
Identification of optimal timing for pregnancy tests

Health Monitoring

Early detection of irregularities or changes
Tracking effects of lifestyle changes or stress
Identifying patterns related to health conditions
Preparing for medical appointments with data

Frequently Asked Questions

What is a normal cycle length?

A normal menstrual cycle typically ranges from 21 to 35 days, with an average of 28 days. However, individual variation is completely normal. Some people naturally have shorter or longer cycles, and this can change throughout their reproductive years. What's most important is understanding your own pattern.

How many cycles should I track for accuracy?

For the most accurate average, track at least 3-6 cycles. The more data you have, the more reliable your average will be. If your cycles are irregular, tracking 6 or more cycles can help identify patterns or determine if you should consult a healthcare provider.

What if my cycles are irregular?

Irregular cycles (varying significantly in length) are common and can be caused by factors like stress, illness, weight changes, or hormonal imbalances. If your cycles vary by more than 7-9 days consistently, or if you miss periods, it's advisable to consult with a healthcare provider to rule out underlying conditions.

How does cycle length affect ovulation prediction?

Ovulation typically occurs about 14 days before the start of the next period in a typical 28-day cycle. For cycles of different lengths, ovulation timing adjusts accordingly. For example, in a 30-day cycle, ovulation would occur around day 16. Knowing your average cycle length helps predict ovulation more accurately.

When should I be concerned about my cycle length?

You should consult a healthcare provider if: your cycles are consistently shorter than 21 days or longer than 35 days, you experience sudden changes in your regular pattern, you miss three or more periods in a row, or you have cycles that vary wildly in length. These could indicate underlying health issues that need attention.

Can I track my cycle length on my phone?

Yes, there are many apps available for tracking menstrual cycles, including our tools here. Digital tracking can be more convenient and allows for better data visualization. However, our calculator provides a simple, private way to calculate your average without needing to install an app or share personal data with third parties.

Cycle Length Calculator — Track Your Menstrual Cycle Regularity