妊娠週数計算機

共有リンク

はじめに

Pregnancy Week Calculator — Calculate your current pregnancy week from your last menstrual period. Enter First day of last period to get an instant, accurate result.

計算式

Gestational age = days elapsed since the first day of the last menstrual period (LMP), converted to weeks and remaining days.

ステップごとの説明

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

実例

Example: With First day of last period = 2026-10-09, the Pregnancy Week Calculator gives Weeks: 0, Days: 0, Total Days: 0.

よくある質問

Why is pregnancy dated from the last period instead of conception?

LMP dating is the standard obstetric convention because the exact conception date is often unknown, while the LMP date is typically recalled more reliably.

How many weeks is a full-term pregnancy?

Full term is generally considered 39-40 weeks from the LMP.

What inputs does the Pregnancy Week 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 Week Calculator?

The Pregnancy Week Calculator applies the formula exactly as calculated — Gestational age = days elapsed since the first day of the last menstrual period (LMP), converted to weeks and remaining days. — 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 Week 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 Week Calculator free to use?

Yes, the Pregnancy Week Calculator is completely free, requires no signup, and runs instantly in your browser.