免费月经周期追踪器
追踪月经周期长度，预测下次月经日期。
days
days
days
Days Until Next Period
13 days
Current Cycle Day15
Ovulation Expected on Day14
PMS Window Starts Day21
Days Until Next Period vs Period Duration
公式
Menstrual Cycle Phases
Typical 28-Day Cycle
Next Period = Cycle Length - Days Since Last Period Ovulation Day = Cycle Length - 14
计算示例
A 28-day cycle, period lasts 5 days, currently on day 15.
- 01Next period in = 28 - 15 = 13 days
- 02Ovulation day = 28 - 14 = Day 14 (just passed)
- 03PMS window starts = Day 21 (in 6 days)
常见问题
What is a normal cycle length?
Normal cycles range from 21 to 35 days. The average is 28 days. Variation of a few days between cycles is normal.
When does PMS start?
PMS symptoms typically begin 7-10 days before the period (during the late luteal phase) and resolve once menstruation starts.
What causes irregular cycles?
Stress, weight changes, exercise, hormonal conditions, birth control, and perimenopause can all cause irregular cycles. Consult a doctor if cycles are consistently outside 21-35 days.
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