Period Calculator
Plan ahead with confidence. Enter the first day of your last period and your usual cycle length to see when your next three periods are likely to arrive.
Period Calculator
Plan ahead with confidence. Enter the first day of your last period and your usual cycle length to see when your next three periods are likely to arrive.
Informational only — not medical advice or a diagnosis. Every pregnancy and cycle is different, and these results are estimates. Always consult your OB-GYN or midwife.
Enter your dates above to see your result.
This is an educational estimate, not medical advice. Consult a qualified professional. For pregnancy and cycle decisions, follow your OB-GYN — guidance reflects the American College of Obstetricians and Gynecologists (ACOG).
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How period prediction works
Your menstrual cycle is counted from the first day of one period to the first day of the next. The average cycle is about 28 days, but anywhere from 21 to 35 days is normal for adults. This calculator simply adds your cycle length to your last start date to project the next three periods.
It also estimates your next ovulation, which typically falls about 14 days before each period begins.
What counts as a normal cycle
Cycle length naturally varies a little from month to month, and many people are not perfectly regular. Factors such as stress, weight change, exercise, travel and approaching menopause can all shift timing. Tracking a few cycles helps you learn your own average and how much it tends to vary.
Because real cycles fluctuate, treat these predictions as a helpful guide for planning rather than exact dates.
When to see a doctor
It’s worth speaking to your OB-GYN if your cycles are consistently shorter than 21 days or longer than 35, if periods suddenly become irregular, if you bleed between periods or after sex, or if bleeding is unusually heavy or painful.
A missed period can signal pregnancy, but also stress, hormonal changes or other conditions. If you might be pregnant, a home test taken after a missed period is a good first step, followed by a chat with your doctor.
Frequently asked questions
What is a normal cycle length?
For adults, a cycle of 21 to 35 days is considered normal, with around 28 days being average. Some month-to-month variation is completely typical.
How accurate are period predictions?
They are estimates based on a regular cycle. Stress, illness, weight change and other factors can shift your dates, so use the predictions as a planning guide.
When should I see a doctor about my periods?
See your OB-GYN if cycles are regularly under 21 or over 35 days, become suddenly irregular, include bleeding between periods, or are unusually heavy or painful.
Sources & references
Not medical advice. This result is an educational estimate from HealthyLifeStyles (Trusted Wellness), based on population formulas — not a diagnosis or treatment. Always consult a qualified healthcare professional about your health.
https://www.healthylifestyles.com/tools/period-calculator