Pregnancy Due Date Calculator
Calculate your expected due date using Naegele's Rule. Get your current gestational week, trimester, and key pregnancy milestones.
Typical range: 21–35 days
Due date = conception date + 266 days
Pregnancy Progress
—T2 starts Week 27
T3 starts Week 40
Key Pregnancy Milestones
Important dates throughout your pregnancy
| Milestone | Week | Approx. Date | Status |
|---|
What is the Pregnancy Due Date Calculator?
The Pregnancy Due Date Calculator estimates your expected delivery date (EDD) using Naegele's Rule — the standard medical formula based on the first day of your last menstrual period (LMP). Pregnancy is counted as approximately 40 weeks (280 days) from the LMP, which is about 38 weeks from conception. The calculator identifies your current gestational week and trimester, and maps out key pregnancy milestones including the end of each trimester, common screening dates, and the viability milestone at 24 weeks. Understanding your due date and gestational age helps you plan prenatal appointments, communicate clearly with your obstetrician, and track your baby's development. The tool also supports conception date and IVF transfer date as input methods. Note that this is an estimate — only about 4% of babies are born exactly on the calculated due date, and a first-trimester ultrasound provides a more accurate gestational assessment.
How to Use the Pregnancy Due Date Calculator
- 1. Select your calculation method: Last Period (LMP), Conception Date, or IVF Transfer Date.
- 2. Enter the relevant date using the date picker.
- 3. If using LMP, enter your average cycle length (default 28 days) for a more personalised estimate.
- 4. For IVF, specify whether a Day 3 or Day 5 (blastocyst) embryo was transferred.
- 5. Click "Calculate Due Date" to see your estimated delivery date, gestational week, trimester, and pregnancy milestones.
How Due Date is Calculated
Naegele's Rule (most common method)
Due Date = LMP + 280 days + (cycle length − 28) days
Standard 28-day cycle → LMP + 280 days (40 weeks)
Only about 4–5% of babies are born exactly on their due date. Normal delivery range is 37–42 weeks. Always consult your doctor or midwife for personalised advice.
Frequently Asked Questions
How accurate is the pregnancy due date?
Only about 4% of babies are born exactly on the estimated due date. Most births occur within 2 weeks before or after the calculated date. A first-trimester ultrasound (10–13 weeks) is more accurate than LMP calculation, especially if cycles are irregular. The due date is best understood as the centre of a normal delivery window spanning 37 to 42 weeks.
What is gestational age?
Gestational age is the length of pregnancy measured from the first day of the last menstrual period (LMP). A full-term pregnancy is 40 weeks of gestational age. This differs from embryonic age (counted from conception), which is approximately 2 weeks less. All clinical pregnancy tracking — milestones, development stages, and medical decisions — uses gestational age in weeks and days.
Can the due date change after an ultrasound?
Yes. If an early ultrasound shows a significant discrepancy from the LMP-based estimate — typically more than 7 days — the doctor may revise the due date. This is common with irregular cycles, uncertain LMP dates, or when conception occurred later than day 14. The ultrasound-based date then becomes the official gestational reference used throughout the pregnancy.
What is the difference between conception date and LMP date?
In a standard 28-day cycle, conception occurs approximately 14 days after LMP. Gestational age counts from LMP, so a pregnancy at 10 weeks gestational age is only 8 weeks from conception. Due dates are calculated from LMP because the exact conception date is often unknown while LMP is easier to recall. This is why gestational age is always about 2 weeks more than embryonic age.