What is cycle length variability?

The cycle length variability was calculated as the average standard deviation of menstrual cycle length for an individual in that age group, meaning that 70% of the menstrual cycles of that individual are expected to vary within that range around the average.

What is a common variation in cycle length?

Variations in cycle lengths are common (4). Within the same year, the length between the longest cycle and the shortest cycle can vary up to 9 days and still be considered within a regular range (5). For example, a common variation can be that one cycle is 25 days long, followed by a cycle that is 33 days long.

Is it normal if a cycle varies far from the average?

A variation that deviates far from the average might be normal for you with no pathological cause, while it might indicate a problem for someone else, and vice versa. The only way to know for sure is to see your healthcare provider if your cycles fall outside of “normal” to make sure there’s no root cause.