Is my period cycle normal?

The "28-day cycle" is a myth

Only 13% of cycles are exactly 28 days. Normal ranges from 21 to 35 days. Variation is the norm.

What's normal

• Cycle length: 21-35 days (average 29.3 days)
• Period duration: 2-7 days (average 5 days)
• Blood loss: 30-40 mL per cycle (about 2-3 tablespoons)
• Variation: Up to 7 days difference between cycles is normal

When to see a doctor

• Cycles shorter than 21 days or longer than 35 days
• Bleeding for more than 7 days
• Soaking through a pad/tampon every hour
• Sudden changes in your established pattern

Sources: ACOG (2024), Bull et al. (2019, NPJ Digital Medicine — 600K cycles analyzed), WHO reproductive health.