What is a Period Calculator?

Period calculator predicts menstrual periods based on cycle length and last period date. Tracks: when next period starts, period duration, cycle pattern. Useful for women planning travel, events, vacations around periods, or tracking irregular cycles (consult doctor if very irregular). Average cycle 28 days; normal range 21-35.

How to use

1. Enter LMP date — First day of last period
2. Cycle length — Days between period starts (default 28)
3. Period duration — How many days bleeding (default 5)
4. View 6-month forecast — Next 6 periods

Tips

• Track 3+ cycles for accurate personal cycle length
• Stress, weight changes, illness can shift cycles
• Apps (Flo, Clue) track over time for accurate predictions
• Irregular cycles (range > 7 days): see gynecologist
• First period after pregnancy: cycles often irregular for months

FAQs

Why does my cycle vary?

Hormones affected by stress, sleep, exercise, weight, diet, medications. 2-4 day variation is normal. Larger swings warrant medical advice.

Ovulation timing?

Approximately 14 days BEFORE next period (regardless of cycle length). For specific tracking, use Ovulation Calculator.

Pregnancy concerns?

Missed period + sexual activity = take pregnancy test (10+ days after expected period). Tool doesn't replace medical advice.

Related

Ovulation Calculator · Pregnancy Week Tracker · Pregnancy Due Date