Period Calculator
Typical range: 21-35 days
Typical range: 3-7 days
Cycle Phases
Menstruation (Days 1-5)
Uterine lining sheds. Bleeding typically lasts 3-7 days.
Follicular Phase (Days 1-13)
Overlaps with menstruation. Follicles develop in ovaries. Estrogen rises.
Ovulation (Day 14)
Egg released from ovary. Most fertile time. Lasts 12-24 hours.
Luteal Phase (Days 15-28)
Progesterone rises. PMS symptoms may occur. Prepares for next cycle.
What's Normal?
Understanding Your Menstrual Cycle
The menstrual cycle is a monthly process that prepares the body for pregnancy. It's regulated by hormones including estrogen, progesterone, FSH, and LH. Understanding your cycle can help with family planning, identifying health issues, and managing symptoms.
Key Hormones
- FSH (Follicle-Stimulating Hormone): Stimulates egg development
- LH (Luteinizing Hormone): Triggers ovulation
- Estrogen: Builds uterine lining, peaks before ovulation
- Progesterone: Maintains uterine lining, rises after ovulation
Signs of Ovulation
- Change in cervical mucus (clear, stretchy, egg-white consistency)
- Slight rise in basal body temperature (0.5-1F after ovulation)
- Mild cramping or twinge on one side (mittelschmerz)
- Breast tenderness
- Increased sex drive
When to See a Doctor
Seek Medical Advice If:
- Periods stop for 3+ months
- Cycles shorter than 21 days
- Cycles longer than 35 days
- Very heavy bleeding
- Severe pain
- Bleeding between periods
Tracking Tips:
- Use an app or calendar
- Note start and end dates
- Track symptoms (cramps, mood)
- Monitor flow heaviness
- Track for 3+ cycles
Factors Affecting Cycle
- Stress: Can delay ovulation and period
- Weight changes: Significant changes affect hormones
- Exercise: Intense exercise can disrupt cycles
- Travel: Time zone changes may affect timing
- Age: Cycles often become irregular near menopause
- Health conditions: PCOS, thyroid issues, etc.
Important Note
This calculator provides estimates based on average cycles. Individual cycles can vary significantly. It should not be used as a sole method of contraception or fertility planning. Consult a healthcare provider for personalized advice.
Frequently Asked Questions
What is a normal menstrual cycle length?
A normal menstrual cycle ranges from 21 to 35 days, with the average being 28 days. Cycle length is counted from the first day of one period to the first day of the next. Variation of a few days between cycles is normal. Cycles shorter than 21 days or longer than 35 days may warrant medical evaluation.
Why is my period late?
Common reasons for a late period include stress, significant weight changes, excessive exercise, travel, illness, hormonal imbalances, approaching menopause, or pregnancy. Occasional irregular periods are normal, but consistently irregular cycles or missed periods for 3+ months should be discussed with a healthcare provider.
What are the phases of the menstrual cycle?
The menstrual cycle has four phases: Menstruation (days 1-5) when the uterine lining sheds, Follicular phase (days 1-13) when follicles develop, Ovulation (around day 14) when an egg is released, and Luteal phase (days 15-28) when progesterone prepares the uterus for possible pregnancy.
Can I get pregnant during my period?
While unlikely, it's possible to get pregnant during your period, especially if you have a short cycle. Sperm can survive up to 5 days in the reproductive tract. If you have a 21-day cycle and have sex near the end of your period, sperm could still be present when you ovulate. No time during the cycle is completely 'safe.'