How accurate is the due date?

It is a population estimate: 60% of births occur within a week of it and ~90% within two weeks. IVF dates are the most accurate, then early ultrasound.

What if I only know my conception date?

Add 266 days — the result is typically within a day or two of the LMP method for regular cycles.

Due Date Calculator

Estimates the delivery date (estimated date of confinement) from your last menstrual period (Naegele's rule), a known conception date or an IVF transfer date, plus gestational age today and a full milestone timeline.

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Live calculate

Presets

Estimate Based On

Last PeriodConception DateIVF Transfer

First Day of Your Last Period

Average Length of Your Cycles

days

Conception Date

IVF Transfer Date

Embryo Age at Transfer

IVF mode only — due date is transfer + 261 days (day 5) or + 263 days (day 3).

Live mode: results update as you type.

Estimated Due Date

August 15, 2027

280 days to go · Naegele rule (LMP + 280 days)

Gestational age today: Before LMP
Current week: Week 1
Trimester: First
Estimated conception: Nov 22, 2026
Full-term window (37–42 wks): Jul 25, 2027 – Aug 29, 2027
LMP used: Nov 8, 2026

Time remaining

Days completed0.00
Days remaining280.00

Pregnancy milestone timeline

Milestone	Date
Last menstrual period (week 0)	Nov 8, 2026
Conception (~week 2)	Nov 22, 2026
End of 1st trimester (13 weeks)	Feb 7, 2027
Viability milestone (24 weeks)	Apr 25, 2027
End of 2nd trimester (27 weeks)	May 16, 2027
Full term begins (37 weeks)	Jul 25, 2027
Due date (40 weeks)	Aug 15, 2027

Only ~4% of babies are born on the estimated due date; ~60% arrive within ±1 week. IVF and early-ultrasound dates are the most precise. Estimates for informational purposes only — not medical advice.

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Formula

Naegele: Due = LMP + 280 days + (cycle − 28) · Conception: Due = conception + 266 · IVF: Due = transfer + 261 (day-5) / 263 (day-3)

• Add 280 days (40 weeks) to the first day of the last menstrual period; adjust by cycle length beyond 28 days.
• A known conception date yields the due date 266 days later (38 weeks of fetal development).
• IVF transfer dates are exact — a day-5 blastocyst is due 261 days after transfer.

Pro tips

• If your cycle is irregular, rely on the first-trimester ultrasound date instead of LMP math.
• The full-term window spans 37w0d to 42w0d — scheduling inductions before 39 weeks carries risks without medical indication.

FAQ

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Due Date Calculator

#due date calculator#pregnancy due date#delivery date estimator#naegele rule#ivf due date

Milestone

Date

Last menstrual period (week 0)

Nov 8, 2026

Conception (~week 2)

Nov 22, 2026

End of 1st trimester (13 weeks)

Feb 7, 2027

Viability milestone (24 weeks)

Apr 25, 2027

End of 2nd trimester (27 weeks)

May 16, 2027

Full term begins (37 weeks)

Jul 25, 2027

Due date (40 weeks)

Aug 15, 2027

Formula

Naegele: Due = LMP + 280 days + (cycle − 28) · Conception: Due = conception + 266 · IVF: Due = transfer + 261 (day-5) / 263 (day-3)

• Add 280 days (40 weeks) to the first day of the last menstrual period; adjust by cycle length beyond 28 days.

• A known conception date yields the due date 266 days later (38 weeks of fetal development).

• IVF transfer dates are exact — a day-5 blastocyst is due 261 days after transfer.