Pregnancy Due Date (EDD) Calculator
Use our free online Pregnancy Due Date Calculator to perform fast, accurate calculations with instant formulas, step-by-step arithmetic, and verified reference benchmarks.
Pregnancy Due Date Calculator
Instant Live Computation • Zero Waiting
Adjust inputs on the left for instantaneous live computation.
How to Calculate: The Pregnancy Due Date Calculator Formula
Naegele's rule calculates the expected delivery date by adding 1 year, subtracting 3 months, and adding 7 days to the first day of the last menstrual period (LMP).
Step-by-Step Calculation Guide
- Select the first day of your Last Menstrual Period (LMP).
- Adjust your average menstrual cycle length (default standard is 28 days).
- Review your estimated date of delivery (EDD).
- Inspect current gestational age and trimester countdown timeline.
Practical Pregnancy Due Date Calculator Examples
LMP: March 1st with standard 28-day cycle.
LMP: March 1st with 32-day cycle (+4 days).
Pregnancy Trimester Milestone Breakdown
Official reference values and benchmark classifications based on standard institutional guidelines.
| Trimester | Gestational Weeks | Key Developmental Focus |
|---|---|---|
| First Trimester | Weeks 1 through 13 | Embryonic organogenesis, heartbeat development, placenta formation |
| Second Trimester | Weeks 14 through 27 | Anatomy scan, fetal movements (quickening), rapid skeletal growth |
| Third Trimester | Weeks 28 through 40+ | Lung maturation, rapid weight gain, preparation for labor and delivery |
| Full Term Window | Weeks 39 through 40 weeks 6 days | Optimal full-term delivery window with lowest complication rates |
Frequently Asked Questions about Pregnancy Due Date Calculator
How accurate are due date calculations?
Only about 4% to 5% of babies are born precisely on their estimated due date. However, over 80% arrive within two weeks before or after the date (between 38 and 42 weeks).
What is gestational age vs fetal age?
Gestational age is measured from the first day of your last period (2 weeks before conception). Fetal age is actual time since conception.
When is an ultrasound due date preferred over LMP?
First-trimester crown-rump length (CRL) ultrasound measurements are considered the medical gold standard if they differ by more than 5 to 7 days from LMP calculations.
What qualifies as full term?
A pregnancy is considered early term at 37–38 weeks, full term at 39–40 weeks, and late term at 41 weeks.