Period Calculator
Predict your next six periods from the first day of your last period, your cycle length and how long your period lasts.
Next period
10 December 2026 Thursday
- Likely to end
- 14 December 2026
- Ovulation before it
- 26 November 2026
Your next period should start around Thursday, 10 December 2026, and last until about 14 December 2026.
How it's worked out
- Next period
12 November 2026 + 28 days10 December 2026 - Ovulation
about 14 days before a period starts26 November 2026
The next six periods
| Starts | Ends | Ovulation before | |
|---|---|---|---|
| 1 | Thu 10 Dec | 14 Dec | 26 Nov |
| 2 | Thu 7 Jan | 11 Jan | 24 Dec |
| 3 | Thu 4 Feb | 8 Feb | 21 Jan |
| 4 | Thu 4 Mar | 8 Mar | 18 Feb |
| 5 | Thu 1 Apr | 5 Apr | 18 Mar |
| 6 | Thu 29 Apr | 3 May | 15 Apr |
- Cycles vary by a few days, and stress, illness and travel shift them. See a doctor if periods are often more than a week off, very painful or very heavy.
How it works
Next period = last period's first day + cycle length · Ovulation ≈ 14 days before the next period
Worked example
With a period starting on 25 October 2026 and a 28-day cycle, the next one is due around Sunday 22 November, lasting until about 26 November, with ovulation around 8 November.
Questions people ask
How do I work out my next period?
Add your usual cycle length to the first day of your last period. A 28-day cycle starting on 25 October gives a next period around 22 November.
What is a normal cycle length?
Anything from about 21 to 35 days is normal for adults, and it can vary a few days from month to month.
When should I see a doctor?
If periods are often more than a week early or late, stop for three months or more without pregnancy, or are very heavy or painful.
About this calculator
Formula and rules last checked 25 October 2026Written and tested by the CalculatorDex teamReport a problem