DeskTray

Period Calculator

Find out when your next period is due and see your coming cycles on a calendar. Your dates stay in your browser.

Runs in your browser. Nothing is uploaded Free, no sign-up Works on mobile
days
From the first day of one period to the day before the next. 28 is common; 21–35 is typical.
days
How many days you usually bleed.

Saved only in this browser’s storage; never sent anywhere. Untick to delete.

Estimates only. These dates assume a regular cycle and a 14-day luteal phase. Real cycles vary with stress, illness, travel, PCOS, thyroid problems, breastfeeding and hormonal medicines. Do not use this as contraception, and do not rely on it to plan or avoid pregnancy. For irregular, very painful or missed periods, see a gynaecologist.

How to calculate your next period

  1. Pick the first day of your last period.
  2. Set your usual cycle and period length.
  3. Read your next periods, check the calendar, or add them to your phone’s calendar.

Features

  • Next six period dates
  • Fertile window and ovulation for each cycle
  • Month calendar with colour and symbols
  • Download as .ics for Google, Apple or Outlook calendar
  • Optional saving on this device only

Frequently asked questions

How is the next period date calculated?

The first day of your last period plus your average cycle length. For a 28-day cycle starting 3 March, the next period is due on 31 March, then every 28 days after that.

What is a normal cycle length?

Anything from 21 to 35 days is common in adults, and it can vary by a few days from month to month. Teenagers and people nearing menopause often have less regular cycles.

My period is late. Should I worry?

A few days late is common, especially with stress, travel or illness. If it is more than a week late and you could be pregnant, take a home pregnancy test. See a doctor if periods stop for three months or more.

Are my dates stored or shared?

No. Everything is calculated in your browser. If you tick “Remember my dates”, they are saved only in this browser’s local storage and are deleted when you untick it.

Can I use this to avoid pregnancy?

No. Calendar predictions are estimates and are not a reliable method of contraception. Talk to a doctor about contraception that suits you.

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