Period Date Calculator
Work out when your next period is due, and the three cycles after it.
Period Date Calculator
Next period starts
25 October 2026
- Next period ends29 October 2026
- Days to go8
- Three cycles after that22 Nov 2026, 20 Dec 2026, 17 Jan 2027
Works out in your browser. Nothing you type is sent anywhere.
In short: Period Date Calculator
From the dates entered, the next period is expected to start around 22 October 2026 and finish around 26 October 2026, which is 8 days away. The three cycles after that would fall around 19 Nov 2026, 17 Dec 2026, 14 Jan 2027. A cycle that varies by a few days either way is entirely normal.
What is Period Date?
A period date estimate projects the next cycles forward from the first day of the last period, using your usual cycle length.
How is Period Date calculated?
Add your usual cycle length to the first day of your last period, and keep adding it for the cycles after that. The end date adds the number of days your period usually lasts.
- nextthe expected first day of the next period
- lastthe first day of your last period
- cycleyour usual cycle length in days
A worked example
| First day of your last period | 24 September 2026 |
|---|---|
| Usual cycle length (days) | 28 |
| Days your period lasts | 5 |
| Result | |
| Next period starts | 22 October 2026 |
| Next period ends | 26 October 2026 |
| Days to go | 8 |
| Three cycles after that | 19 Nov 2026, 17 Dec 2026, 14 Jan 2027 |
Every figure in this table is produced by the same calculation the tool above runs.
How to use this period date calculator
- Enter the first day of your last period.
- Enter your usual cycle length, from one first day to the next.
- Enter how many days your period usually lasts.
- Read the next date, and the three cycles after it.
Questions people ask
How is cycle length counted?
From the first day of one period to the day before the next one starts, not from the day bleeding stops. Mixing those two up is the most common reason a prediction looks wrong. Most cycles fall somewhere between three and five weeks.
Why is my period late when the tool says otherwise?
Because a calendar projection assumes every cycle is the same length, and real cycles vary with stress, illness, travel, exercise and weight change. A difference of a few days is usual. A period that is very late, or several that are, is worth a doctor's attention.
Can I use this to avoid pregnancy?
No. Calendar methods are unreliable for contraception because ovulation can shift, and this tool should not be used for that purpose. Speak to a doctor about methods that actually work. The ovulation tool is for planning a pregnancy, not preventing one.
Is anything I type here saved or shared?
No. Everything is worked out inside your browser, nothing is stored, and this tool will never put your dates into a link or an image. Only the page's own address can be shared.
Accuracy and sources
For general information. Not medical advice.
Checked by the Daytoolz team on 16 October 2026. How we check our tools.
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