排卵日計算機
最も妊娠しやすい日と排卵期を予測します。
排卵日
から-
精密な妊娠計画
排卵は通常、次の生理が始まる14日前に起こります。最も妊娠しやすい日は、排卵日を含むその前5日間です。
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Estimating Your Fertile Window and Ovulation Day
概要
Ovulation is when an ovary releases an egg, and the days around it are the most fertile of the cycle. This calculator estimates your likely ovulation day and fertile window from your last period and cycle length, in your browser. It is a guide, not a contraception or fertility guarantee.
使い方（ステップ）
- 1
Enter your last period date
The first day of your most recent period.
- 2
Enter your cycle length
The average number of days from one period to the next.
- 3
Read your fertile window
The tool highlights the estimated ovulation day and surrounding fertile days.
仕組み
Ovulation typically occurs about 14 days before the next period starts, so the tool counts backward from your estimated next period based on cycle length. The fertile window spans roughly the five days before ovulation plus the ovulation day itself, because sperm can survive several days. Cycle variability means these are estimates; ovulation tests or temperature tracking add precision.
こんなときに使う
Identifying the days most likely for conception. Understanding your cycle for family planning. Tracking your fertile window alongside other signs.
よくある質問
Calendar estimates are not reliable contraception because ovulation timing varies. Use a proven contraceptive method if preventing pregnancy is the goal.
注意事項
Fertility-window predictions are estimates and are not a reliable form of contraception or medical advice. Cycles vary — consult a qualified healthcare provider for family-planning or fertility guidance.