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受胎日計算機

最終月経から推定受胎日と出産予定日を算出。

はじめに

Pregnancy Conception Calculator — Estimate your conception date and due date from your last period. Enter First day of last period to get an instant, accurate result.

計算式

Estimated conception date = LMP + 14 days (standard obstetric estimate assuming a ~28-day cycle with ovulation around day 14). Due date = LMP + 280 days (Naegele's rule).

ステップごとの説明

  1. Enter the First day of last period.
  2. Click Calculate to see your result instantly.

実例

Example: With First day of last period = 2026-10-09, the Pregnancy Conception Calculator gives Estimated Conception: 2026-10-23, Due Date: 2027-07-16.

よくある質問

Why is conception estimated at 14 days after the LMP?
Ovulation typically occurs around day 14 of a standard 28-day cycle, so conception is estimated near that point.
Is this accurate for irregular cycles?
This estimate assumes an average cycle length; if your cycles are irregular or longer/shorter than 28 days, actual conception timing may differ.
What inputs does the Pregnancy Conception Calculator need?
You'll need to provide: First day of last period. All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Pregnancy Conception Calculator?
The Pregnancy Conception Calculator applies the formula exactly as calculated — Estimated conception date = LMP + 14 days (standard obstetric estimate assuming a ~28-day cycle with ovulation around day 14). Due date = LMP + 280 days (Naegele's rule). — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is this a medical diagnosis?
No. The Pregnancy Conception Calculator provides an estimate based on standard formulas and general population data, not a medical diagnosis or personalized clinical advice. Individual results can vary — consult a doctor or other qualified healthcare provider for medical concerns.
Is the Pregnancy Conception Calculator free to use?
Yes, the Pregnancy Conception Calculator is completely free, requires no signup, and runs instantly in your browser.

受胎日計算機について

The Pregnancy Conception Calculator uses a real, verifiable formula — Estimated conception date = LMP + 14 days (standard obstetric estimate assuming a ~28-day cycle with ovulation around day 14). Due date = LMP + 280 days (Naegele's rule). — so results are accurate every time, not an approximation.