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Due Date Calculator

Estimate your pregnancy due date from your last period, conception date, ultrasound, or IVF transfer — with the estimated conception date and early, full, and late-term windows.

Maintained by CalculatorBuddy TeamEditorial methodology

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Last Period

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

October 8, 2026

Estimated result

Estimated conception date
January 15, 2026

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Compare scenarios

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

Term windows

TermBegins
Early term (week 37)September 17, 2026
Full term (week 39)October 1, 2026
Late term (week 41)October 15, 2026
Post-term (week 42)October 22, 2026
Estimated due dateOctober 8, 2026

Calculate an estimated due date from a last period, conception date, ultrasound measurement, or IVF transfer. The result table shows when ACOG term categories begin.

Examples

LMP January 1, 2026; 28-day cycle

The estimated due date is October 8, 2026. Early term begins September 17, full term begins October 1, late term begins October 15, and post-term begins October 22.

Day-5 transfer January 15, 2026

The estimated due date is October 3, 2026: transfer date + 261 days.

Formula

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

Use the due date documented by your prenatal clinician for medical decisions. This tool cannot determine whether an ultrasound should revise an earlier date.

Sources

Choose the pregnancy timeline you need

For an estimated week-by-week timeline from a dating method, open the Pregnancy Calculator. To work backward from a due date toward possible conception dates, use the Pregnancy Conception Calculator. These calendar estimates cannot identify a specific conception event or establish paternity.

Frequently asked questions

How is the estimated due date calculated?
LMP mode adds 280 days plus a cycle-length adjustment. Conception mode adds 266 days. Ultrasound mode projects from gestational age at the scan, while IVF mode uses transfer date and embryo age.
Is the result a clinical due date?
No. It reproduces the selected arithmetic. A clinician may use ultrasound and clinical redating criteria to establish the best obstetric estimate.
What are the term ranges?
ACOG defines early term as 37 weeks 0 days through 38 weeks 6 days, full term as 39 weeks 0 days through 40 weeks 6 days, late term as week 41, and post-term as 42 weeks or later.

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