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CalculatorBuddy

Pregnancy Calculator

Estimate your due date and track how far along you are from your last period, conception date, ultrasound, IVF transfer, or a known due date — with conception date, trimester, and key milestone dates.

Maintained by CalculatorBuddy TeamEditorial methodology

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ExampleSample values — edit any field to see your result.

days

Days from the start of one period to the next (default 28).

Results update as you type.

Estimated due date

Third trimester

October 8, 2026

Estimated result

You are
41 weeks 2 days pregnant
Estimated conception date
January 15, 2026
Time to due date
Overdue by 1 week 2 days

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Compare scenarios

Keep a baseline, then change an assumption to see its effect side by side.

Key dates

MilestoneDate
Estimated conceptionJanuary 15, 2026
End of first trimester (week 13)April 8, 2026
End of second trimester (week 27)July 15, 2026
Early term begins (week 37)September 17, 2026
Full term begins (week 39)October 1, 2026
Estimated due date (week 40)October 8, 2026
Estimated due dateOctober 8, 2026

Estimate a due date, gestational age today, trimester, conception date, and key dates from the information available. The result is an estimate for planning; prenatal care should use the due date documented by the clinician.

Examples

Last period January 1, 2024; 28-day cycle

The estimated due date is October 7, 2024 and estimated conception is January 15. On March 15 the calculated gestational age is 10 weeks 4 days. Early term begins September 16 and full term begins September 30.

Formula

Last period: EDD = LMP + 280 days + (cycle length − 28)
Conception:  EDD = conception + 266 days
Ultrasound:  EDD = scan date + (280 − gestational age at scan)
IVF:         EDD = transfer date + 266 − embryo age

ACOG recommends setting the estimated due date as soon as reliable LMP or ultrasound information is available and changing it only rarely. A simple calculator cannot apply all clinical redating rules.

Term dates shown

The milestone table marks early term at 37 weeks, full term at 39 weeks, and the estimated due date at 40 weeks. These labels describe gestational-age ranges; they do not predict when labor will begin.

Sources

Frequently asked questions

How is an estimated due date calculated?
The last-period mode adds 280 days and adjusts for cycle length. Other modes use a conception date, ultrasound gestational age, IVF transfer, or an existing due date.
Which dating method is most reliable?
ACOG states that first-trimester ultrasound is the most accurate method to establish or confirm gestational age. ART pregnancies should use the embryo age and transfer date.
What does full term mean?
ACOG defines early term as 37 weeks through 38 weeks 6 days and full term as 39 weeks through 40 weeks 6 days. Late term begins at 41 weeks and post-term at 42 weeks.

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