When is my next period?
A menstrual cycle runs from the first day of one period to the first day of the next. Add your usual cycle length to the start of your last period and you have the start of the next one. The calculator does this for the next 12 cycles and also shows when you are likely to ovulate and your fertile days in each.
Example: a period that began on March 1, 2027, with a 28-day cycle and 5-day periods, means the next periods start on March 29, April 26 and May 24, 2027.
What is a normal cycle?
For adults, cycles from 21 to 35 days are normal, and periods usually last 2 to 7 days. Cycles are often longer and less regular in the first years after periods begin and in the years before menopause. A cycle that changes by a few days from month to month is common.
When to see a doctor
- Your periods stop for more than 90 days and you are not pregnant.
- Cycles are shorter than 21 days or longer than 35 days.
- A period lasts more than 7 days, or bleeding is very heavy.
- You bleed between periods or have severe pain.
Frequently asked questions
Why is my period late?
Stress, illness, travel, changes in weight or exercise, breastfeeding and some medicines can delay a period. If there is a chance you are pregnant, take a test.
How do I find my average cycle length?
Note the first day of each period for a few months, count the days between them and take the average.
Does the calculator work with irregular cycles?
It gives a rough guide, but the more your cycles vary, the less precise the dates. A period tracking app with several months of data helps.