How does the LMP dating method work?

The calculator corrects the LMP by cycle length if needed, then adds 280 days to estimate the due date.

When should ultrasound replace LMP dating?

Use ACOG discrepancy thresholds: small first-trimester differences can matter, while later pregnancy requires larger differences to change the estimated due date.

How is IVF due date calculated?

The due date is calculated from transfer date and embryo age using standard IVF/ART dating conventions.

LoanPay Logic

Pregnancy Due Date & Milestone Calculator

Home Tools CenterPregnancy Due Date & Milestone Calculator

Elite pregnancy tool

Pregnancy dating, milestone tracking, and ACOG-style calibration in one elegant page.

Use LMP, ultrasound, known EDD, IVF/ART, or conception date inputs to estimate the due date, gestational age, and estimated conception date with premium medical-grade presentation.

Method

LMP

Today

May 30, 2026

Status

Ready to calculate

Real imagery

Authentic medical and maternal imagery pulled from unsplash image URLs.

Calculator controls

Choose your dating method

LMP first dayCycle length

ACOG discrepancy thresholds

Ultrasound timing	Re-date if off by
Single CRL ultrasound before 9 weeks	≥ 5 days
Single CRL ultrasound 9w0d to 13w6d	≥ 7 days
Second-trimester ultrasound 14w0d to 21w6d	≥ 10 days
Second-trimester ultrasound 22w0d to 27w6d	≥ 14 days
Third-trimester ultrasound 28w0d and later	≥ 21 days

Results

Estimated due date, gestational age, and conception date

Ready for calculation

Enter the values above and click Calculate to reveal your due date, gestational age, and conception estimate.

Important dates & windows

Timeline of pregnancy milestones

6 weeks

Early ultrasound may confirm a gestational sac and embryo development.

10 weeks

NIPT and first-trimester screening commonly become available.

14 weeks

Second trimester begins; energy often improves.

20 weeks

Anatomy ultrasound is usually scheduled around this window.

28 weeks

Third trimester starts; glucose screening and Rh checks are commonly reviewed.

40 weeks

Estimated due date reached, though delivery commonly occurs before or after.

How calibration works

Perinatology-style decision logic

LMP dating uses corrected LMP = LMP + (cycle length − 28), then EDD = corrected LMP + 280 days.

Ultrasound dating can override LMP when the discrepancy exceeds accepted thresholds by gestational age.

IVF/ART uses transfer date and embryo age to estimate due date precisely.

Conception dating adds 266 days from the estimated conception day.

ACOG calibration table

When to re-date the pregnancy

Ultrasound window	Threshold for changing EDD
Single CRL ultrasound before 9 weeks	≥ 5 days
Single CRL ultrasound 9w0d to 13w6d	≥ 7 days
Second-trimester ultrasound 14w0d to 21w6d	≥ 10 days
Second-trimester ultrasound 22w0d to 27w6d	≥ 14 days
Third-trimester ultrasound 28w0d and later	≥ 21 days

These thresholds are presented as a practical clinical reference and are aligned with widely used ACOG-style dating principles.

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