To calculate your next period, enter the first day of your last period and add your average cycle length. Most cycles range from 21 to 35 days. For example, a March 1 period with a 28-day cycle points to an expected next period around March 29.
FAQ
Frequently Asked Questions
These answers are written to match common search intent around period timing, fertile days, ovulation, late periods, and cycle regularity. Expand any question for a direct answer.
You are usually most fertile during the 6 days leading up to and including ovulation day. In a 28-day cycle, ovulation often happens around day 14, so the fertile window commonly falls around days 9 to 14.
Pregnancy during your period is less likely, but it can still happen. Sperm may survive for up to 5 days, so people with shorter cycles or earlier ovulation may still conceive if intercourse happens during bleeding.
A normal menstrual cycle is typically 21 to 35 days long when measured from the first day of one period to the first day of the next. The average is often described as 28 days, but regularity matters more than hitting that exact number.
Period calculators are most accurate for people with regular cycles. When timing is consistent, predictions are often useful within a few days. Irregular cycles, stress, illness, travel, postpartum changes, and hormone-related conditions reduce accuracy.
A late period can happen because of stress, major weight change, illness, travel, intense exercise, hormonal shifts, PCOS, thyroid issues, medication changes, or pregnancy. If your period is more than a few days late and that is unusual for you, track it closely and consider medical advice.
The fertile window is the 6-day span ending on ovulation day. It includes the 5 days before ovulation and ovulation day itself, because sperm can survive for several days before an egg is released.
Speak to a doctor if your cycles are consistently shorter than 21 days or longer than 45 days, if you miss 3 or more periods in a row, or if you notice heavy bleeding, severe pain, or large month-to-month shifts.
A period is generally considered late when it has not started within a few days of your expected date. If your cycles are regular, even a 5-day delay may feel significant. Tracking several months helps you see what is normal for you.
An early period may happen because you ovulated earlier than usual, or because stress, travel, illness, or hormone changes altered your cycle. A one-off early period is common, but repeated shifts are worth tracking.
Yes. Stress can affect the hormonal signals that help regulate ovulation, which can delay both ovulation and the next period. When ovulation happens later, the period usually arrives later as well.
To estimate fertile days, first predict ovulation, then count the 5 days before it plus ovulation day. In a 28-day cycle, ovulation often happens around day 14, so fertile days usually fall around days 9 to 14.
The luteal phase is the part of the cycle after ovulation and before the next period. It often lasts around 12 to 14 days, and it is usually more consistent than the earlier part of the cycle.
Many people ovulate about 14 days before the next period starts. That timing can vary, but it is the common rule period calculators use to estimate ovulation and fertile days.
Yes. A 28-day cycle is well within the normal adult range of 21 to 35 days. It is often used as the default example, but shorter or longer regular cycles can also be normal.