Power Calculators

🌸 Next Period Date Calculator

Calculate your estimated next menstrual period date using the first day of your last period and your average menstrual cycle length.

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Enter details

Enter the first day of your most recent menstrual period.
Enter the average number of days from the first day of one period to the first day of the next period.
Estimated Next Period
Sat, 31 Jan 2026

Chart


Also available in our Android app, with charts and full breakdown tables.

📘 About the Next Period Date

The Next Period Date Calculator estimates when your next menstrual period may begin.

It uses the first day of your most recent menstrual period and your average menstrual cycle length.

The first day of menstrual bleeding is counted as day 1 of the menstrual cycle.

The calculator adds your average cycle length to the first day of your last period to estimate the beginning of your next period.

Because menstrual cycles can naturally vary, the calculated date should be treated as an estimate rather than an exact prediction.

🧮 Formula

Next period calculation
Estimated Next Period = First Day of Last Period + Average Cycle Length

Where

  • Last Period = first day of your most recent menstrual period
  • Cycle Length = average number of days from the first day of one period to the first day of the next period
  • Next Period = estimated first day of the next menstrual period
The estimated next period date is calculated by adding the average menstrual cycle length to the first day of the last menstrual period.

✏️ Worked examples

Example 1 - 28-Day Cycle

You enter
First Day of Last Period1 Jan 2026
Average Menstrual Cycle Length28 days
You get
Estimated Next PeriodThu, 29 Jan 2026

If the first day of your last period was January 1 and your average cycle length is 28 days, your estimated next period will begin around January 29.

Try this example →

Example 2 - 30-Day Cycle

You enter
First Day of Last Period1 Jan 2026
Average Menstrual Cycle Length30 days
You get
Estimated Next PeriodSat, 31 Jan 2026

If the first day of your last period was January 1 and your average cycle length is 30 days, your estimated next period will begin around January 31.

Try this example →

Example 3 - 26-Day Cycle

You enter
First Day of Last Period1 Feb 2026
Average Menstrual Cycle Length26 days
You get
Estimated Next PeriodFri, 27 Feb 2026

If the first day of your last period was February 1 and your average cycle length is 26 days, your estimated next period will begin around February 27.

Try this example →

🧭 How to use this calculator

What you enter

  • First Day of Last PeriodEnter the first day of your most recent menstrual period.
  • Average Menstrual Cycle Length (days)Enter the average number of days from the first day of one period to the first day of the next period.

What you get

  • Estimated Next Period

💡 How to Use This Calculator

  • Enter the first day of your most recent menstrual period.
  • Enter your average menstrual cycle length in days.
  • Your cycle length is counted from the first day of one period to the first day of the next period.
  • The calculator adds your cycle length to the date of your last period.
  • The result is your estimated next menstrual period date.

💡 Understanding Your Menstrual Cycle

  • The menstrual cycle begins on the first day of menstrual bleeding.
  • Cycle length is measured from the first day of one period to the first day of the following period.
  • A 28-day cycle is commonly used as an example, but individual cycle lengths can be different.
  • Your own average cycle length is generally more useful for estimation than automatically assuming a 28-day cycle.
  • Cycle length can vary from one month to another.

💡 Why Your Next Period May Be Earlier or Later

  • Stress can affect menstrual timing.
  • Changes in sleep, exercise, body weight or daily routine may affect the menstrual cycle.
  • Illness and some medications can affect menstrual timing.
  • Hormonal contraception can change bleeding patterns.
  • Pregnancy and breastfeeding can change or stop menstrual periods.
  • Perimenopause can cause changes in cycle length and menstrual timing.

💡 How Accurate Is the Calculator?

  • The calculator provides an estimated date rather than an exact prediction.
  • The calculation assumes that your future cycle will be approximately the same length as the average cycle length you entered.
  • If your cycle varies significantly from month to month, the actual period date may differ from the calculated date.
  • Tracking several menstrual cycles can help you determine your typical cycle length.

💡 When to Consider Medical Advice

  • Consider speaking with a qualified healthcare professional if your periods are consistently very irregular.
  • Seek appropriate medical advice if your usual menstrual pattern changes significantly.
  • Very heavy bleeding, severe menstrual pain, bleeding between periods or other concerning symptoms may require medical evaluation.
  • If your period is late and pregnancy is possible, consider an appropriate pregnancy test.

💡 Important Disclaimer

  • This calculator is for informational and educational purposes only.
  • It does not provide a diagnosis or medical advice.
  • The estimated date cannot guarantee when your next menstrual period will occur.
  • Menstrual cycles naturally vary between individuals and from cycle to cycle.
  • For personal medical concerns, consult a qualified healthcare professional.

❓ Frequently asked questions

How do I calculate my next period date?

Enter the first day of your last menstrual period and your average cycle length. The calculator adds the cycle length to the first day of your last period to estimate your next period date.

What is the first day of the menstrual cycle?

The first day of menstrual bleeding is generally counted as day 1 of the menstrual cycle.

What is a normal menstrual cycle length?

Menstrual cycle length can vary between individuals. A 28-day cycle is commonly used as an example, but your own cycle may be shorter or longer.

Can this calculator predict my exact next period date?

No. It provides an estimate based on your previous cycle information. Menstrual cycles can naturally vary from month to month.

What if my periods are irregular?

If your cycle length varies significantly, a single average cycle length may not accurately predict your next period. Tracking several cycles can help you determine your typical cycle pattern.

Can stress affect my period date?

Yes. Stress and changes in routine can affect menstrual timing in some people, so the actual period date may be earlier or later than the calculated estimate.

Can I use this calculator if my period is already late?

You can use the calculator to compare the expected date with the current date, but it cannot determine why a period is late. If pregnancy is possible, consider an appropriate pregnancy test and seek professional medical advice when needed.

Can this calculator tell me if I am pregnant?

No. A next-period calculator cannot diagnose pregnancy. If pregnancy is possible and your period is late, use an appropriate pregnancy test and consult a healthcare professional when needed.

What happens if my cycle is 30 days instead of 28 days?

The calculator uses the cycle length you enter. For example, entering a 30-day cycle will estimate the next period approximately 30 days after the first day of your last period.

Is the first day of bleeding used as the last period date?

Yes. Enter the first day of your most recent menstrual bleeding, which is counted as cycle day 1.

What people are saying
★★★★★
Anonymous · 30 Sep 2026