Menstrual Cycle Calculator

Count forward from the first day of your last period by your average cycle length (typically 21-35 days, with 28 being average). For example, if your last period started January 1st and your cycle is 28 days, your next period would be expected around January 29th.

A normal menstrual cycle ranges from 21 to 35 days, with the average being 28 days. Cycles can vary by a few days from month to month. If your cycle is consistently shorter than 21 days or longer than 35 days, consult a healthcare provider.

Your fertile window typically occurs around ovulation, which happens approximately 14 days before your next period starts. The fertile window spans about 5 days before ovulation through 1 day after. For a 28-day cycle, this is roughly days 10-15.

Period calculators provide estimates based on average cycle patterns. They are most accurate for people with regular cycles. Stress, illness, travel, and other factors can affect cycle timing. For the most accurate predictions, track your cycles over several months.

A period that is a few days late is usually normal, as cycles naturally vary. Common causes include stress, changes in weight or exercise, travel, and illness. If your period is more than 7 days late and you could be pregnant, consider taking a pregnancy test. If consistently irregular, consult a healthcare provider.