Why is my period cycle a different number of days every month?
It's common for cycle length to vary by several days from month to month — a spread of up to about 7–9 days across cycles is within the typical range for many adults.
簡短回答
Menstrual cycle length is counted from the first day of one period to the first day of the next. For adults, a cycle of 21–35 days is generally considered within a typical range; in adolescents, more variation is common. Stress, illness, significant weight changes, sleep disruption, and travel can all affect ovulation timing, which shifts the cycle length. Cyca's Insights screen shows your personal average cycle length (calculated from your last 6 logged cycles), your average period duration, and your variation (expressed as ± days) — giving you a concrete, data-driven picture of your own pattern over time. A variation of ±4 days or less shows as 'regular'; a wider spread is flagged as 'variable', which may be worth tracking more closely. If your cycle is consistently outside the 21–35 day range, or if it changes suddenly without a clear reason, that's worth discussing with a healthcare provider.
先用真實範例試試 Cyca，決定前請確認目前 App Store 頁面上的確切功能與價格。
挑選前要注意什麼
- Cycle length = day 1 of period to day 1 of the next period (not from end to start)
- Typical adult range: 21–35 days; variation of ±7 days across cycles is common
- Ovulation timing shifts first — cycle length changes follow from this
- An app averages your recent cycles to make predictions; logging at least 3–6 cycles improves accuracy
- Consistently <21 days, >35 days, or sudden unexplained changes deserve a healthcare conversation
實用的決策步驟
- 先確定你最常需要完成的任務。
- 用真實內容或實際情境測試 App。
- 查看隱私標籤與帳號需求。
- 確認匯出與備份選項。
- 選擇你願意長期維持的定價模式。
快速比較
| 需求 | 要確認什麼 | 為什麼重要 |
|---|---|---|
| 定價模式 | 確認實用功能是需要訂閱、一次性解鎖,還是都不用。 | 第一天最便宜的 App,一年後不一定最便宜。 |
| 隱私模式 | 內容敏感時,優先選在裝置上處理的 App。 | 私人文件、履歷、學習資料與家庭內容,都值得謹慎對待。 |
| 匯出/綁定 | 確認檔案格式、分享、備份與刪除的控制權。 | 好的 App 應該幫你完成任務,而不是把你的成果綁死。 |
Cyca 適合哪些情境
Cyca 正是為這類需求打造——請使用上方檢查清單，並用真實範例測試。
隱私無廣告裝置端處理
這是由 App 開發團隊親自撰寫的購買指南。App Store 的功能與價格可能會有變動，請在購買前至商店頁面確認詳細資訊。
常見問題
How does Cyca calculate my average cycle length?
It measures the interval between each pair of consecutive logged period starts, filters outliers (gaps under 15 or over 60 days), takes your most recent up to 6 cycles, and averages them. Until you've logged at least 2 periods, it uses your manually-entered setting as the default.
What does the '±' variation number mean in the Insights screen?
It's the difference between your shortest and longest recent cycle length. A variation of ±4 days or less is shown as 'regular'; a larger spread indicates more variability in your pattern.
My cycle runs about 32 days — is that a problem?
Cyca is not a medical tool and cannot tell you whether your cycle length is clinically significant. A 32-day cycle is within the commonly cited adult range of 21–35 days. Any concerns about your cycle — length, regularity, symptoms — should be discussed with a qualified healthcare provider.