Period Calculator: Next Periods

Predict your next periods for the coming months from the first day of your last period, cycle length and period length. Enter your values; the result updates as you type, with the method shown below.

About this calculator

Knowing when your next period is due helps you plan holidays, sport and appointments. From the first day of your last period, your cycle length and the length of your period, this calculator predicts the next six periods and estimates ovulation.

Enter the first day of your last period, your cycle length and the number of days your period lasts. The calculator shows the next period, the estimated ovulation and the next six periods.

When to use it

Planning holidays and events.
Tracking cycle regularity.
Preparing a doctor’s appointment.
Knowing when to expect symptoms.

How to read the result

Next period = first day of last period + cycle length. A 28-day cycle starting on 8 November gives a next period on 6 December.

Cycles vary by a few days; regularly very irregular or painful periods are worth discussing with a doctor. This is not a method of contraception.

Mistakes to avoid

Using it as contraception.
Using an average cycle length that does not reflect your own.
Ignoring big changes in your cycle.

Formula

Next period = first day of last period + cycle length

Worked example

28-day cycle starting 8 November: next period 6 December.

Frequently asked questions

What if my cycle is irregular?

Use your average cycle; predictions will be less precise.

Can it prevent pregnancy?

No, it is not a method of contraception.

What is a normal cycle?

Usually between 21 and 35 days in adults.

Why does my period come early or late?

Stress, travel, illness and weight changes can shift it.

When should I see a doctor?

If cycles are very irregular, very painful or stop without explanation.

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Results are estimates for information only. Check important figures with a professional.