Pregnancy Due Date Calculator: EDD and Timeline

When will your baby arrive? Doctors date most pregnancies from the first day of the last period. They last about 40 weeks. The Pregnancy Due Date Calculator estimates your due date and how far along you are. It also lists milestone dates.

It suits expecting parents who want a first estimate before a prenatal visit. The date is an average, not a promise. Your doctor or midwife sets the official due date.

Table of Contents

• What the Calculator Does
• How to Use It, Step by Step
• The Due Date Formula
• Worked Example
• How to Read the Results
• Choosing the Right Method
• Limitations and Assumptions
• FAQs About the Pregnancy Due Date Calculator

What the Calculator Does

The tool offers three ways to start. Each one reaches the same 40 week timeline.

• Estimated Due Date: the date 280 days after the first day of your last period.
• Gestational Age: weeks and days between that start date and today.
• Current Trimester and Days Remaining until the due date.
• A Progress bar and a milestone table with ten rows.
• Copy Timeline and Export CSV buttons for the milestone table.

How to Use It, Step by Step

1. Pick a Calculation Method: Last Menstrual Period (LMP), Conception Date, or IVF Transfer Date.
2. For LMP, choose the First Day of Last Period and your Average Cycle Length (Days). Dates start empty, and the cycle box starts at 28.
3. For conception, choose the Conception Date.
4. For IVF, choose the Transfer Date. Then pick the Embryo Age: Day 3, Day 5, or Day 6.
5. Press Calculate Due Date and read the cards and table. Every card reads N/A until a valid date is entered.

The Due Date Formula

The LMP method follows Naegele's rule. It adds 280 days to the first day of the last period. That is close to one year minus three months plus seven days.

• LMP method: start = last period + (cycle length - 28) days.
• Conception method: start = conception date - 14 days.
• IVF method: start = transfer date - (14 + embryo age) days.
• Due date = start + 280 days. Gestational days = today - start.
• Milestone dates add 14, 28, 97, 98, 140, 168, 195, 196, 259, and 280 days to the start.

Worked Example

Nia's last period began on Jan 12, 2026. Her cycle is 28 days, so no adjustment applies. Her start date is Jan 12, and 280 days later is Oct 19, 2026.

On Mar 9, 2026, that is 56 days after the start. The tool shows 8w 0d, the 1st Trimester, and 224 days remaining. Progress reads 20%.

If her cycle were 32 days, the start moves forward 4 days. The due date becomes Oct 23, 2026. A Day 5 IVF transfer on Feb 1, 2026 gives Oct 20, 2026. A Day 3 transfer on the same day gives Oct 22, 2026.

How to Read the Results

The Estimated Due Date is the center of a long window. Most babies arrive between about week 37 and week 42. Only a small share are born on the exact date.

Gestational Age counts from the start date, not from conception. So a pregnancy called 8 weeks old began only about 6 weeks ago.

The first trimester runs from 0w0d to 13w6d. The second runs from 14w0d to 27w6d, and the third starts at 28w0d. Sources draw these lines a little differently.

After the due date, the Days Remaining card reads "Due date passed" with the number of days ago. Dates in the future, or more than 42 weeks old, give a message instead.

The milestone table is a rough guide. The example above shows seven of its ten rows. It also lists the Week 24 Milestone, Second Trimester Ends, and Third Trimester Starts. Your own prenatal schedule may differ.

Choosing the Right Method

Use LMP when you know your period date and have fairly regular cycles. Use conception if you tracked ovulation. Use the IVF option if you know the transfer date and embryo age.

An early ultrasound can refine the date. Doctors often use it when periods are irregular or the date is unknown. If it differs from the calculator, follow your provider's date.

If you are still planning, try the ovulation calculator. Once your baby is born, the baby growth calculator offers a rough growth guide. Needs change in pregnancy. See also the water intake calculator and the ideal sleep duration calculator. Blood type often comes up at prenatal visits, so the blood type compatibility checker may help. More tools are in the health and fitness calculators hub.

Limitations and Assumptions

• The result is an average. Full-term pregnancies vary by several weeks.
• The LMP method assumes ovulation about 14 days before the next period, adjusted by cycle length.
• The tool does not use ultrasound measurements, twins, or any health condition.
• The cycle length must be a whole number from 20 to 45. It cannot plan a future transfer date.
• Milestone dates and trimester labels are general. Your clinic may use different weeks.
• Do not use it for medical decisions. Always confirm dates with your doctor or midwife.

FAQs About the Pregnancy Due Date Calculator

This calculator gives general estimates only and is not medical advice. Reviewed for general accuracy by Prof. Dr. Khalil Mudassar, PhD.