Menstrual Cycle Calculator
Know when your next period is due, when you're likely to ovulate and which days are less fertile, and keep track of your cycles over time.
How a cycle works
This is an example 28-day cycle. Enter the first day of your last period above to see your own dates.
- Period
- Safe period
- Fertile
- Ovulation
- Next period
- Ovulation
- Safe period (lower chance of pregnancy)
- Fertile days
- Periods after that
Your calendar
| Sun | Mon | Tue | Wed | Thu | Fri | Sat |
|---|
- Period
- Safe period
- Fertile
- Ovulation
- Today
Cycle tracking
Add the date each period started. Once you have two or more cycles, the calculator uses your own average and range instead of a typical cycle.
No periods logged yet. Enter your last period above, then add earlier ones here.
| Period started | Cycle length | Remove |
|---|
About the safe period
The safe period is worked out with the calendar method: days outside your possible fertile window. It lowers the chance of pregnancy but does not remove it.
- It is not reliable contraception on its own. Ovulation can come early or late because of stress, illness, travel or weight change.
- It works best with regular cycles that you have tracked for at least 6 months.
- Don't rely on it after childbirth, while breastfeeding, after stopping hormonal contraception, or as you approach menopause.
- It doesn't protect against sexually transmitted infections.
- Ask your doctor about contraception that suits you if you need to avoid pregnancy.
What's a normal cycle?
- Every 24 to 38 days. Day 1 is the first day of proper bleeding, not spotting.
- Varies by 7 to 9 days or less between your shortest and longest cycles.
- Bleeding lasts up to 8 days.
- It's normal for cycles to be less regular in the first few years after periods start and in the years before menopause.
When to see a doctor
- your periods come more often than every 24 days, or less often than every 38 days
- your cycle length changes by more than 7 to 9 days from month to month
- bleeding lasts more than 8 days, or you soak a pad every 1 to 2 hours or pass clots bigger than a ₹10 coin
- you bleed between periods or after sex
- you have severe period pain that stops you doing everyday things
- your periods stop for 3 months or more and you're not pregnant
- you bleed after menopause