Pregnancy Due Date Calculator — Two ways to estimate a due date. The default is Naegele's rule: due date = first day of last period + 280 days (40 weeks). This works if your cycles are roughly 28 days. If you know the conception date (IVF transfer, known ovulation, IUI), use that mode — it adds 266 days instead.
Your dates never leave the browser.
Dates are estimates for general information only, not medical advice. Only a clinician's ultrasound-based dating is reliable. Contact your healthcare provider for anything concerning your pregnancy.
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Pregnancy Due Date Calculatorとは？
Two ways to estimate a due date. The default is Naegele's rule: due date = first day of last period + 280 days (40 weeks). This works if your cycles are roughly 28 days. If you know the conception date (IVF transfer, known ovulation, IUI), use that mode — it adds 266 days instead.
The calculator shows the current week and day, which trimester you're in, days until the due date, and the key milestone dates (heartbeat detectable at 7 weeks, anatomy scan at 20 weeks, viability at 24 weeks, full term at 37 weeks).
使い方
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Pick the input mode
LMP (last menstrual period) or known conception date.
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Pick the date
For LMP: the first day of your most recent period. For conception: the date of ovulation, IUI, or embryo transfer.
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Read the result
See the due date, current week/day, trimester, and milestone dates.
使用例
LMP on January 1
Standard 28-day cycle.
結果： Due date: October 8
Conception on February 14
Known timing.
結果： Due date: November 7 (266 days later)
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Last reviewed: 2026-09-25