Calculate your estimated due date based on last menstrual period. Track pregnancy milestones.
Estimate your baby's delivery date.
The Due Date Calculator estimates your baby's expected arrival using Naegele's Rule, the standard medical method for calculating the estimated date of delivery (EDD). Based on your last menstrual period (LMP), this calculator determines when you've reached 40 weeks of pregnancy—the average length of human gestation from the start of the last period.
Understanding your due date helps you plan for your baby's arrival and track important developmental milestones throughout pregnancy. However, it's important to remember that only about 4-5% of babies arrive exactly on their due date. A "full term" pregnancy ranges from 37 to 42 weeks, with most babies arriving within two weeks of the estimated date. Your healthcare provider may adjust your due date based on ultrasound measurements, especially if your cycle is irregular.
Pregnancy is typically divided into three trimesters, each with distinct developmental changes. The first trimester (weeks 1-12) involves organ formation, the second trimester (weeks 13-27) sees rapid growth and movement, and the third trimester (weeks 28-40) focuses on brain development and weight gain in preparation for birth.
This assumes a 28-day cycle with ovulation on day 14. Adjust for longer/shorter cycles.
| Trimester | Weeks | Key Developments |
|---|---|---|
| First | 1-12 | Organ formation, heartbeat detectable |
| Second | 13-27 | Movement felt, gender visible, rapid growth |
| Third | 28-40 | Brain development, lungs mature, weight gain |
| Early Term | 37-38 | Baby is considered full term |
| Full/Late Term | 39-41 | Optimal delivery window |
LMP of June 1, 2024: Due Date = June 1 + 280 days = March 8, 2025. First trimester ends around August 24, second trimester ends around November 30.
Related tools: Pregnancy Weight Gain Calculator for healthy weight tracking, Ovulation Calculator for family planning, and BMI Calculator for health assessment.
Naegele's Rule: LMP + 280 days (40 weeks). Or: LMP - 3 months + 7 days + 1 year. Assumes 28-day cycle with ovulation on day 14. Ultrasound may adjust date.
Only 4-5% of babies arrive on due date. Full term is 37-42 weeks. Most babies come within 2 weeks of EDD. First ultrasound provides most accurate dating.
Weeks = days since LMP ÷ 7. Pregnancy is dated from last menstrual period, not conception (which is ~2 weeks later). At positive test you're typically 4-5 weeks.