Use this Expected Day of Delivery calculator to estimate your due date using one of three common methods: last menstrual period (LMP), conception date, or IVF transfer date.
Estimated delivery is typically around 40 weeks of pregnancy, but normal birth can occur before or after this date.
How the expected day of delivery is estimated
Most due-date tools use standard obstetric formulas to estimate when a pregnancy will reach 40 weeks. This estimate is useful for planning appointments, screening windows, and general pregnancy milestones. The important thing to remember is that a due date is a target, not a guaranteed birthday.
Only a small percentage of babies are born on the exact calculated date. Many healthy pregnancies deliver in a broader window around that date. Think of the result as a planning anchor rather than a fixed deadline.
Methods used in this calculator
1) Last menstrual period (LMP) method
This is the most common method. It starts from the first day of your last period and adds 280 days (40 weeks). If your cycle is longer or shorter than 28 days, the estimate is adjusted accordingly.
2) Conception-date method
If you know your conception date, the calculator adds 266 days. This approach can be helpful when ovulation timing is known with confidence.
3) IVF transfer-date method
For IVF pregnancies, due date estimation is generally more precise because the embryo age and transfer date are known. The calculator adjusts based on whether a day-3 or day-5 embryo was transferred.
What your result includes
- Estimated due date (EDD): Your projected 40-week date.
- Current gestational age: Approximate weeks and days pregnant based on the selected method.
- Delivery window: A practical range from 37 to 42 weeks, where many normal births happen.
- Countdown: Days remaining until the estimated due date.
Why due dates can change
Even with accurate inputs, estimated delivery dates can shift based on clinical findings. Early ultrasound is often used to confirm or adjust dating, especially if menstrual cycles are irregular or the LMP is uncertain.
Other factors that may affect actual delivery timing include first pregnancy status, maternal health, fetal growth patterns, and spontaneous labor timing.
Tips for using this tool effectively
- Use exact dates when possible for best accuracy.
- If your cycles are irregular, rely on medical dating from your care team.
- Recheck your estimate after your first-trimester ultrasound.
- Use the result for planning, not for self-diagnosis.
Frequently asked questions
Is this calculator medically diagnostic?
No. It is an educational estimator and cannot replace prenatal care or professional medical advice.
How accurate is an estimated due date?
It is usually accurate enough for planning, but exact birth timing varies significantly. Clinical confirmation is always recommended.
What if I do not know my LMP?
If you know conception or IVF transfer date, use those methods. Otherwise, your provider can date the pregnancy with ultrasound.