Pregnancy Due Date Calculator – When Is Your Baby Due?
A pregnancy due date calculator estimates when your baby will arrive based on the first day of your last menstrual period (LMP). The standard method, known as Naegele's rule, adds 280 days (40 weeks) to your LMP date. If your cycle is longer or shorter than the typical 28 days, the estimate is adjusted accordingly. While only about 5% of babies arrive exactly on their due date, knowing the estimated date helps you plan prenatal care, prepare for delivery, and track which trimester you are in. This article explains how due dates are calculated and links to our free Pregnancy Due Date Calculator.
Quick Answer
| Label | Value |
|---|---|
| Method | Naegele's rule (LMP + 280 days) |
| Cycle adjustment | Added for cycles longer than 28 days |
| Typical pregnancy | 40 weeks (280 days) |
| Accuracy | Most births occur within 2 weeks of EDD |
How It Works
Due date = LMP date + 280 days + (cycle length - 28). The calculator starts with the first day of your last menstrual period, adds 280 days (the average gestation), then adjusts for your cycle length. A 30-day cycle adds 2 extra days; a 26-day cycle subtracts 2. It also calculates your current week of pregnancy, which trimester you are in, and days remaining. Use our Pregnancy Due Date Calculator to enter your LMP date and cycle length for a personalized estimate.
Additional Notes
This is an estimate. Your healthcare provider may adjust the due date based on ultrasound measurements. Always consult your doctor for medical decisions.
Use Our Calculator
Try our Pregnancy Due Date Calculator for your own numbers: /calculators/pregnancy-due-date-calculator
Related Calculators
About 5% of babies arrive on their exact due date. Most arrive within 1-2 weeks before or after. Your doctor may adjust based on ultrasound.
An early ultrasound can estimate gestational age. Consult your healthcare provider for the most accurate dating.
Longer cycles mean later ovulation, pushing the due date later. Shorter cycles mean earlier ovulation and an earlier due date. The adjustment is the difference from 28 days.