Support article
When is my next period
Use a simple date rule to estimate your next period, then use a period calculator when you want a faster answer and a cleaner monthly timeline.
Article body
Answer the search intent clearly, then guide the user back into the calculator flow.
Start with the first day of the last period
#Most people estimate the next period by taking the first day of the last period and adding their usual cycle length. If your cycle is usually 28 days and your last period started on April 1, the next period is expected around April 29.
This estimate works best when your cycle is fairly steady. It gives you a planning anchor for travel, appointments, and symptom tracking.
Use cycle length, not bleeding length
#The cycle length is the number of days from one period start date to the next. It is different from period length, which only counts the bleeding days.
- Count from the first day of bleeding, not the last day.
- Use the cycle length that feels most common in the last few months.
- Expect some movement if life has been busy or your body feels different this month.
Use a calculator when you want the full monthly picture
#If you want a faster answer, a period calculator can estimate the next period, ovulation day, and fertile window together. That fuller view is easier to use than doing the math by hand every month.
If your cycle changes a lot from month to month, a range-based calculator for irregular periods is the better fit.
Get your next date in one step
If you want the fastest answer, use the main calculator with the first day of your last period and your usual cycle length.
Start with the broad monthly forecast for your next period, ovulation, and fertile window.
FAQ
Cover the follow-up questions people usually have around this topic.
What date matters most for estimating the next period?
Start with the first day of your last period, then add your usual cycle length. That gives you the expected next start date.
Which cycle length should I use?
People often use a typical cycle length from the last few months, such as 26, 28, or 30 days.
Why can the next period arrive earlier or later?
Stress, travel, illness, sleep changes, and hormonal shifts can all move the expected date.
Reviewed guidance
Date-estimate pages should show where the timing logic comes from
Next-period estimates are most useful as educational forecasts built from the first day of the last period and recent cycle length. Visible sources make the planning boundary clear.
Office on Women's Health: Your menstrual cycle
Cycle basics, first-day counting, and when irregular timing deserves extra attention.
Open official sourceNHS: Missed or late periodsPlain-language guidance on common causes of late or missed periods and when to seek care.
Open official sourceOffice on Women's Health: Period problemsPatient guidance on missing periods, irregular timing, and symptom-led escalation.
Open official source