Use this pregnancy due date calculator to estimate your EDD (Estimated Due Date) either from your last menstrual period (LMP) or from your current gestational age in weeks and days.
Medical note: this tool gives an estimate only. Your healthcare provider may adjust your due date based on ultrasound and clinical findings.
How this EDD calculator by weeks works
This due date calculator estimates when you are most likely to reach 40 weeks of pregnancy. Most calculators use a 280-day pregnancy length (40 weeks) counted from the first day of your last period. If you already know your gestational age (for example from a scan), the calculator works backward to find the expected due date.
Keep in mind that only a small percentage of babies are born exactly on their due date. Most healthy deliveries happen between 37 and 42 weeks.
Two ways to estimate your due date
1) From LMP (last menstrual period)
This is the classic method, often called Naegele’s rule: add 280 days to the first day of your last menstrual period. It works best for people with regular 28-day cycles and a known LMP date.
2) From weeks pregnant (gestational age)
If you know exactly how far along you are (for example 22 weeks and 3 days), this method can be more practical. The calculator subtracts your current gestational age from 280 days, then adds the remaining days to your reference date.
What your results include
- Estimated Due Date (EDD): your projected 40-week date.
- Estimated gestational age today: useful for tracking progress.
- Estimated conception date: around 2 weeks after LMP in many cycles.
- Pregnancy milestones: start of second trimester, third trimester, and full term (37 weeks).
Pregnancy week milestones (quick guide)
- Week 12: first trimester nearing completion.
- Week 14: second trimester begins.
- Week 20: halfway point of pregnancy.
- Week 28: third trimester begins.
- Week 37: early term / full term window begins.
- Week 40: estimated due date.
When estimates can change
Your EDD may be revised during prenatal care. Common reasons include:
- Irregular menstrual cycles or uncertain LMP date
- Early ultrasound measurements that suggest a different gestational age
- Assisted reproduction timing (IUI/IVF)
Important reminder
This calculator is designed for planning and educational use. It does not diagnose pregnancy conditions. If you have pain, bleeding, decreased fetal movement, or urgent concerns, contact your maternity provider immediately.