Calculate Your Cycle

First day of your last period:

Average menstrual cycle length:

Average period length:

Luteal phase length (optional): Days between ovulation and next period

Your Menstrual Cycle Predictions

Next Period Start:

Current Cycle Day:

Ovulation Date:

Fertile Window:

Menstrual Cycle Timeline

Menstruation

Follicular Phase

Ovulation

Luteal Phase

Tracking Tips

For best results, track your actual period start dates for 3-6 months to determine your true average cycle length. Your cycle may vary due to stress, travel, illness, or other factors.

Understanding Your Menstrual Cycle

The menstrual cycle is the monthly hormonal cycle a woman's body goes through to prepare for pregnancy. The average cycle is 28 days, but normal cycles can range from 21 to 35 days.

How the Period Calculator Works

This calculator predicts your future periods by:

Counting forward from your last period start date
Using your average cycle length to project future dates
Estimating ovulation and fertile days based on typical patterns
Adjusting for your personal period duration

Phases of Your Menstrual Cycle

Menstruation (Days 1-5): Shedding of the uterine lining
Follicular Phase (Days 6-13): Follicles in ovaries mature
Ovulation (Day 14 in 28-day cycle): Egg is released
Luteal Phase (Days 15-28): Uterus prepares for possible pregnancy

Benefits of Tracking Your Period

Predict when your next period will start
Identify your fertile window for conception
Notice patterns in PMS symptoms
Detect irregularities that may need medical attention
Plan events around your cycle

Frequently Asked Questions

The calculator is very accurate for women with regular cycles. Accuracy depends on how consistent your cycle length is. If your cycles vary by more than a few days each month, the predictions may be less precise. Tracking your actual periods for several months will improve the predictions.

For irregular cycles, the calculator can still provide estimates, but they may be less reliable. Consider tracking additional signs like basal body temperature, cervical mucus, or using ovulation predictor kits. If your cycles are consistently irregular (varying by more than 7-9 days), consult a healthcare provider.

While the calculator can identify your likely fertile window, the calendar method alone is only about 76-88% effective for preventing pregnancy. For better protection, combine with other methods like barrier contraception or fertility awareness methods that track basal body temperature and cervical mucus.

Cycle length can vary due to:

Stress or emotional changes
Significant weight loss or gain
Excessive exercise
Travel or changes in routine
Medical conditions like PCOS or thyroid disorders
Perimenopause (in older women)

Occasional variations of a few days are normal, but consistent irregularity may warrant medical advice.

Period Calculator