Period Calculator
Track your menstrual cycle, predict next period, and identify fertility windows
Calculate Your Menstrual Cycle
Typical range: 21-35 days (average: 28 days)
Typical range: 3-8 days (average: 5 days)
Select the first day of your last menstrual period
Menstrual Cycle Predictions
Current Cycle Phase
Next Period Starts
Next Period Ends
Fertility Window
Highest chance of pregnancy during this 8-day window
Cycle Analysis
Medical Disclaimer
This period calculator provides estimates based on average cycle patterns and should not be used as the sole method for contraception or fertility planning. Menstrual cycles can vary significantly between individuals and can be affected by stress, illness, travel, and other factors. For medical concerns about your menstrual cycle, contraception, or fertility, please consult with a qualified healthcare provider.
Menstrual Cycle Phases
Menstrual Phase
Days 1-5 (approx.)
Shedding of uterine lining
Follicular Phase
Days 1-13 (overlaps with menstrual)
Egg development in ovaries
Ovulation
Around day 14
Egg release from ovary
Luteal Phase
Days 15-28
Uterine lining thickens
Period Tracking Tips
Track your cycle for 3-6 months for better predictions
Note cycle length variations (normal range: ±7 days)
Record symptoms like cramps, mood changes, flow intensity
Consider using period tracking apps for detailed monitoring
Consult healthcare provider for irregular cycles
Understanding Your Menstrual Cycle
How Period Prediction Works
Period calculators use your average cycle length and the date of your last period to predict when your next period will start. The calculation assumes your cycle follows a regular pattern, though natural variations are completely normal.
Normal Cycle Variations
- •Cycle length: 21-35 days (28 days average)
- •Period duration: 3-8 days (5 days average)
- •Flow: 30-40ml total blood loss per cycle
- •Variation: ±7 days from average is normal
Fertility Window Calculation
Ovulation: Typically occurs 14 days before next period
Fertility Window: 7 days before to 1 day after ovulation
Total Duration: 8 days of potential fertility
When to See a Doctor
- Irregular cycles: Consistently shorter than 21 or longer than 35 days
- Heavy bleeding: Soaking through a pad/tampon every hour
- Severe pain: Debilitating cramps affecting daily activities
- Missed periods: No period for 3+ months (if not pregnant)