OmniTools

Pregnancy Due Date Calculator

Estimate due date, pregnancy weeks, and trimester milestone timelines.

Basis: Naegele's rule (LMP + 280 days) and ACOG Committee Opinion 700 on estimating due date·2026-08-28 verified·Not reviewed by a medical professional·Editorial policy

Before you rely on this

Estimated by adding 280 days to the first day of the last menstrual period. Late ovulation or a cycle other than 28 days shifts the result, and fewer than 5% of births occur on the estimated date. An ultrasound-dated gestational age supersedes this, and the tool does not replace antenatal care.

Tool Overview & Key Purpose

Calculate estimated due date (EDD), gestational age, trimester stage, and fetal development milestones.

Step-by-Step Usage Instructions

1STEP 1

Choose calculation method (Last Menstrual Period - LMP, Conception Date, or Ultrasound).

2STEP 2

Input the date and average cycle length (default 28 days).

3STEP 3

Discover estimated due date, current gestational weeks + days, and countdown D-day.

4STEP 4

Review trimester milestones and key medical checkup timelines.

Real-World Scenarios & Practical Cases

3 Practical CasesScenario #1

LMP January 10th Due Date Calculation

With a 28-day cycle, estimated due date is October 17th. On April 1st, gestational age is 11 weeks + 4 days (1st Trimester).

Uses Naegele's rule modified for personal cycle variations.Scenario #2

Prenatal Medical Checkup Planning

Schedule nuchal translucency scan (weeks 11-13), quad screen (weeks 16-18), and glucose screening (weeks 24-28).

Never miss key diagnostic windows.Scenario #3

Maternity Leave Scheduling

Calculate exact countdown to plan workplace maternity leave filing dates effectively.

Coordinate leave starting 2-4 weeks prior to due date.Gestational age and due date basisNaegele's Rule: Due Date = LMP Month - 3 Months + 7 Days + (Cycle - 28 Days)

Pro Tips & Key Considerations

Ultrasound measurements in the first trimester provide the most accurate medical due date.Only ~5% of babies are born exactly on their due date; full-term delivery spans weeks 37 to 41.

Frequently Asked Questions (FAQ)

Sources & References

ACOG — How Your Fetus Grows During Pregnancy Mayo Clinic — Pregnancy Due Date Calculator

Basis: Naegele's rule (LMP + 280 days) and ACOG Committee Opinion 700 on estimating due date · 2026-08-28 verified