Pregnancy Due Date Calculator
Estimate your due date, see your current weeks and days, and explore a week-by-week guide of your pregnancy.
A pregnancy calculator estimates your due date, current gestational age, and trimester based on your last menstrual period or conception date. While due dates are estimates — only about 5% of babies arrive on their exact due date — knowing your timeline helps you plan prenatal care and prepare for delivery.
Examples
Calculate with LMP
Frequently Asked Questions
How accurate is the due date?
Key Terms
- Gestational Age
- The age of a pregnancy counted from the first day of the last menstrual period, measured in weeks and days.
- LMP (Last Menstrual Period)
- The first day of the most recent menstrual period, used as the standard starting point for calculating gestational age.
- Trimester
- One of three roughly equal periods of pregnancy: first (weeks 1-13), second (weeks 14-27), and third (weeks 28-40).
- EDD (Estimated Due Date)
- The predicted date of delivery, typically calculated as 280 days (40 weeks) from the first day of the LMP.
- Viability
- The point at which a fetus can survive outside the womb, generally around 24 weeks of gestation with intensive medical care.
References
- Calculating Your Due Date — American College of Obstetricians and Gynecologists (ACOG)
- Prenatal Care — U.S. Department of Health & Human Services
Quick Tips
- •Confirm your estimated due date with an early ultrasound (8-12 weeks) for the most accurate dating.
- •Think of your due date as a due window — most babies arrive between 38 and 42 weeks.
- •Track your prenatal appointments by gestational week, as doctors measure pregnancy progress this way.
- •Download a pregnancy tracking app to monitor weekly milestones and development.
A pregnancy calculator estimates your due date, current gestational age, and trimester based on your last menstrual period or conception date. While due dates are estimates — only about 5% of babies arrive on their exact due date — knowing your timeline helps you plan prenatal care and prepare for delivery.
How to Use This Calculator
Enter either your last menstrual period (LMP) date, your conception date, or information from an ultrasound, depending on what you know. Click Calculate to get an estimated due date, your current week and day of pregnancy, and which trimester you are in. Always confirm dates with your healthcare provider.
Understanding the Formula
Due Date = LMP + 280 days. Trimesters are divided into Week 1-13, 14-27, and 28-40.
Examples
Calculate with LMP
If your last period started on January 1, your estimated due date would be October 8.
Frequently Asked Questions
How accurate is the due date?
Only about 5% of babies are born on their actual due date. It is an estimate.
Assumptions & Limitations
- Based on a standard 28-day menstrual cycle; women with longer or shorter cycles may have different actual due dates.
- The Naegele rule (LMP + 280 days) assumes ovulation on day 14 of the cycle, which varies between individuals.
- Ultrasound dating, especially in the first trimester, is generally more accurate than LMP-based estimates.
- Does not account for individual variations in fetal development or medical conditions that may affect timing.
Key Terms
- Gestational Age
- The age of a pregnancy counted from the first day of the last menstrual period, measured in weeks and days.
- LMP (Last Menstrual Period)
- The first day of the most recent menstrual period, used as the standard starting point for calculating gestational age.
- Trimester
- One of three roughly equal periods of pregnancy: first (weeks 1-13), second (weeks 14-27), and third (weeks 28-40).
- EDD (Estimated Due Date)
- The predicted date of delivery, typically calculated as 280 days (40 weeks) from the first day of the LMP.
- Viability
- The point at which a fetus can survive outside the womb, generally around 24 weeks of gestation with intensive medical care.
References
- Calculating Your Due Date — American College of Obstetricians and Gynecologists (ACOG)
- Prenatal Care — U.S. Department of Health & Human Services