---
title: Period Calculator: Predict Your Next Period
description: Free menstrual period calculator. Predict your next three periods, ovulation and PMS window from your last period and cycle length.
url: https://niyora.com/tools/period-calculator/
---

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- Period calculator: when is my next period?

Free tool

# Period calculator: when is my next period?

Your next three periods, ovulation and PMS window, from the first day of your last period and your usual cycle length.

Loading the calculator…

## How to calculate your next period

Count your cycle from the **first day of bleeding** to the day before your next period starts. Add that number to the first day of your last period and you have your next one.

If your cycle is 28 days and your last period started on the 3rd, your next one is due on the 31st. The calculator does the same, three cycles ahead, and marks ovulation about 14 days before each period.

## What counts as a normal cycle?

Anything from **21 to 35 days** is typical for adults, and a few days of variation from month to month is normal. Periods usually last 2 to 7 days. Stress, travel, illness, weight change and starting or stopping contraception can all shift a cycle.

Talk to a doctor if your cycles are often shorter than 21 days or longer than 35, if you skip three periods in a row, or if bleeding lasts more than a week.

## Why the days before matter

For many people the period itself isn’t the hard part. The week before is. That is when PMS shows up as irritability, tears, anxiety or rage. The calculator shows that window too, so you can see it coming.

When the window arrives

Niyora predicts your PMS window from your own cycles, then helps with the hard moment itself.

## Questions people ask

How do I calculate my period cycle?

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Count from the first day of one period to the day before the next one starts. That number is your cycle length. Most cycles run between 21 and 35 days.

Can stress delay my period?

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Yes. Stress can delay ovulation, which pushes your period later. A period a few days late after a stressful month is common. If it is very late and you could be pregnant, take a test.

Is this calculator accurate for irregular periods?

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Less so. It assumes a steady cycle length. If your cycle varies a lot, use your average and treat the dates as a rough guide.

## More free tools

[PMS calculator: see when your hard days start](https://niyora.com/tools/pms-calculator/)[Luteal phase calculator](https://niyora.com/tools/luteal-phase-calculator/)[Ovulation calculator: when do I ovulate?](https://niyora.com/tools/ovulation-calculator/)

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