How does the is my period normal? work?
- Cycle length: FIGO calls 24 to 38 days normal for adults. In the first few years after periods start, 21 to 45 days is common (ACOG).
- Regularity: a difference of up to 7 to 9 days between your shortest and longest cycle counts as regular (FIGO).
- Period length: bleeding for up to 8 days is within the normal range.
- Flow, pain and unexpected bleeding: we flag the signs the NHS says are worth seeing a GP about.
Normal is a range, not a number
Only about 13% of cycles in a study of more than 600,000 were exactly 28 days long (Bull, 2019). Guidelines describe a range instead. For adults, FIGO calls 24 to 38 days normal, with bleeding for up to 8 days. Teens often have cycles of 21 to 45 days while things settle (ACOG).
The best answer comes from tracking
Memory is fuzzy, especially about dates. Logging a few periods, even just start dates, gives you something solid. Our cycle length calculator turns start dates into your average and range.
When to see a doctor
- Bleeding after menopause, between periods or after sex.
- Periods that are very heavy or painful, or last more than 8 days.
- Periods that stop for 3 months, or cycles under 21 or over 35 days apart.
In the UK you can call NHS 111 for advice, any time. In an emergency call 999 (UK) or 911 (US).
Questions people ask
What is a normal period?
For adults, a period every 24 to 38 days, lasting up to 8 days, with a flow that doesn't take over your life. Most cycles vary a little month to month.
Is it normal for periods to be irregular as a teen?
Yes. Cycles of 21 to 45 days are common in the first few years, and they usually settle. If periods haven't started by 15, or are very far apart, see a GP (ACOG).
When should I see a GP about my periods?
If your periods are very heavy or painful, last over 8 days, come less than 21 days apart or more than 35, change a lot, stop for 3 months, or you bleed between periods, after sex or after menopause.
Is bleeding after sex normal?
It can have simple causes, but it should be checked by a GP, especially if it keeps happening.
Is this a diagnosis?
No. It's a structured way to notice patterns and decide whether, and how soon, to talk to someone. Only a clinician can diagnose, usually with an examination and sometimes tests.
Is anything I enter saved or sent?
No. Everything runs in your browser. Nothing is stored or sent, and the page makes no network requests when you use it.
Sources
Written by the Splash team · Sources checked Oct 2026 · Updated
