Start with the first day you saw blood, even if it was just spotting. Add your usual cycle length to estimate your next period. If you do not know your cycle length yet, use 28 days as a starting estimate.
Made for Teens
Period Calculator for Teens
Track your cycle, predict your next period, and find out if your cycle is normal — built specifically for teens who are new to their period.
💜 First things first: irregular periods are completely normal for the first 2-3 years after your period starts. You're not broken. Your body is still figuring things out.
FreePrivateNo sign-upMade for teens
Reviewed by Dr. Sarah Mitchell, MD · Pediatric & Adolescent Gynecology · Updated March 2026
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Frequently Asked Questions
Frequently Asked Questions
Yes. Irregular periods are very common for the first 2-3 years after your first period because your hormones are still finding a rhythm.
Many teen periods last 2-7 days. If bleeding lasts more than 10 days, or you feel weak or dizzy with heavy bleeding, talk to a doctor.
A teen cycle can commonly range from about 21-45 days, especially in the first few years. Adults are often closer to 21-35 days.
Teen periods can be late because your cycle is still regulating. Stress, illness, sports, weight changes, sleep changes, and travel can also affect timing.
Write down Day 1, the last day of bleeding, how heavy it was, pain level, and any symptoms. A notes app, calendar, or private tracker all work.
Some people start later than others, but if you are 15 and have not had your first period, it is a good idea to talk to a doctor.
Skipping occasionally can be normal in the first 1-2 years. If you often skip 2 or more months, or it has been more than 3 years since your first period, mention it at a checkup.
Mild or moderate cramps are common. Cramps that make you miss school, throw up, faint, or stop normal activities are worth talking to a doctor about.
Yes, teens can use tampons if they want to. It can take practice. Change tampons every 4-8 hours and never leave one in for more than 8 hours.
Heavy flow can be common, but soaking through a pad or tampon in under an hour for several hours is not something to ignore. A doctor can help.
PCOS is a hormone-related condition that can cause irregular periods, acne, and extra hair growth. It is common and manageable, but only a clinician can diagnose it.
Related Tools
Related Tools
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Safe Period Calculator
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Normal Cycle Guide
Read more about what cycle ranges can be normal.
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Irregular Period Guide
Learn why periods can be irregular and when to ask for help.
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Sources
Medical references and methodology
This page is educational and does not replace medical advice. It uses teen-friendly language and the reviewer label for this page is Pediatric & Adolescent Gynecology. Last reviewed: March 17, 2026.