Enter the first day of your last menstrual period. Due date is estimated using Naegele's rule (LMP + 280 days).
Major organs forming; fingers and toes developing.
Embryo implants in uterine wall
Heart begins to beat
Major organs forming
Risk of miscarriage drops significantly
May be visible on ultrasound
Detailed ultrasound; halfway point
Survival possible with intensive care
Eyes open; rapid brain development
Practice breathing movements
Baby moves into head-down position
Considered early term delivery
Estimated delivery date
This tool is part of these guided projects. Each project provides step-by-step instructions with checklists and all the tools you need in one place.
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Calculate due date from last menstrual period (LMP). Estimate weeks pregnant and days to go. Based on 40-week pregnancy.
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The standard method adds 280 days (40 weeks) to the first day of the last menstrual period (LMP). Assumes a 28-day cycle with ovulation on day 14.
Due Date = LMP + 280 days (or LMP + 7 days − 3 months + 1 year)Pregnancy is measured from LMP, not conception. Gestational age is typically 2 weeks ahead of fetal age.
Gestational Week = (Current Date − LMP) ÷ 7The Pregnancy Due Date Calculator performs date math using the proleptic Gregorian calendar. Leap years follow the standard 4/100/400 divisibility rules.
Days = End Date − Start DateUpdated: July 2026
Calculating estimated due date at the first obstetric appointment.
→ Due date: ~October 22, 2026 (40 weeks)
Determining which trimester and key milestones at 24 weeks gestation.
→ Second trimester (weeks 14–27), viability milestone reached
A project manager uses the Pregnancy Due Date Calculator to count working days between today and a milestone, excluding weekends and holidays.
Medical gestational age starts from LMP, not conception. If you know conception date, add 2 weeks to get gestational age. Due date from conception = conception + 266 days.
Only ~5% of babies arrive on the due date. Normal full-term delivery ranges from 37–42 weeks. The due date is an estimate, typically adjusted by early ultrasound.
Use our free Pregnancy Due Date Calculator for fast, accurate results in your browser. No signup or installation required — works on any device.