How do you know if your period is regular or irregular? I can't figure mine out! – Laura* We sometimes use the words "monthly cycle" to describe periods — but that can make it seem as if all periods happen like clockwork every 4 weeks! The truth is, different girls have different cycles. A girl's cycle is the number of days from the start of her period to the start of the next one. On average, it's 28 days. But cycle lengths vary — some girls have a 24-day cycle, some have a 34-day cycle. It's common for girls to skip periods or have periods come at different times, especially in the first few years after beginning menstruation. Other things that affect cycles include diet, stress, exercise, and, occasionally, illness. Try not to worry if you can't figure out your cycle for the first couple of years after you start getting your period. Things should settle down eventually. But if your period isn't coming regularly, if it's very uncomfortable or heavy, or if it's stopped, see a health care provider. *Names have been changed to protect user privacy. Back to Articles Related Articles Irregular Periods Wondering whether it's normal to have irregular periods? Get the facts about this common problem. Read More All About Periods Periods can be confusing. Get the facts in this article for teens. Read More PMS, Cramps, and Irregular Periods Get the facts on which period problems are normal and which ones might indicate something's going on. Read More Is it OK to Get My Period Twice in One Month? Find out what the experts have to say. Read More Should I Take Pills to Regulate My Period? Find out what the experts have to say. Read More I'm 19. Is it Normal to Still Have Irregular Periods? Find out what the experts have to say. Read More Can a Girl Get Pregnant if Her Periods Are Irregular? Find out what the experts have to say. Read More Did My Period Stop Because of Too Much Exercise? Find out what the experts have to say. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.