About the Period Calculator
Know when your next period is due. Enter the first day of your last period, your cycle length and how long your period lasts to see the next six periods.
Key features
- Next period date
- The following five periods
- Current day of your cycle
- Period end dates
- Estimated ovulation
- Private: nothing is stored
Predict your next period
Plan ahead for holidays, events and sport. Enter the first day of your last period, your average cycle length and how long your period usually lasts.
How it's calculated
Next period = First day of last period + cycle length
A last period on 1 October with a 28-day cycle means the next is expected on 29 October, then 26 November, 24 December, and so on.
Normal ranges
| Typical | |
|---|---|
| Cycle length | 21–35 days |
| Period length | 2–7 days |
| Ovulation | About 14 days before the next period |
Related calculators
Ovulation calculator, pregnancy due date calculator, and holiday countdown.
How to use the Period Calculator
- Enter your numbers in the fields above. Units and options can be changed at any time.
- The result updates instantly as you type; there's no calculate button to press.
- Check the breakdown under the main result for the details behind the number.
- Adjust the inputs to compare scenarios, for example a different rate or term.