Find your cycle length from the dates your periods started.
Average cycle length
Some dates are in the future. These results describe the dates you entered, not a prediction.
| Period start | Next start | Days |
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What does cycle length mean?
Cycle length is the number of days from the start of one period to the start of the next. If your period starts on 1 March and the next starts on 29 March, that cycle is 28 days long. It is not the number of days you bleed.
Methodology
The calculator puts your dates in order and counts calendar days between each pair of period starts. The average is the total of those cycle lengths divided by the number of cycles, shown to one decimal place when needed. The range is your shortest to longest recorded cycle.
Two period starts give one cycle length. More dates let you compare several cycles. If you miss a period entry, the gap may include more than one cycle. These results describe your records; they do not predict ovulation, diagnose a condition or determine whether you are pregnant.