Period Calculator
Next several periods from your cycle length.
Next period
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How the Period Calculator works
A menstrual cycle is counted from the first day of one period to the first day of the next. Cycles between 21 and 35 days are considered normal, and a variation of a few days month to month is entirely typical.
Not medical advice. This calculator gives a general estimate, not medical advice. It cannot account for your individual health, medical history, or medication. Talk to a qualified healthcare professional before acting on any result.
Frequently asked questions
What is a normal cycle length?
21 to 35 days for adults, and up to 45 days in the first years after menarche. Consistency matters more than the exact figure — a stable 32-day cycle is unremarkable, while one swinging between 24 and 38 days is worth discussing with a clinician.
What are the phases of the menstrual cycle?
Menstrual (days 1-5), follicular (day 1 to ovulation), ovulation (around mid-cycle), and luteal (ovulation to the next period). The follicular phase absorbs most of the variation between people; the luteal phase is relatively fixed at 12-16 days.
Why is my period late?
Common causes include stress, significant weight change, intense training, illness, travel across time zones, and hormonal contraception changes. Pregnancy is the obvious one to exclude. Persistent irregularity, especially with other symptoms, warrants medical review.
How many periods will this predict?
Several cycles ahead, but confidence falls with each one, because prediction assumes your cycle length stays constant. Tracking actual dates over several months gives a far better average than a single reported figure.