How to Calculate Your Due Date

Using Your Last Menstrual Period (LMP)

The LMP method is the most common way doctors estimate a due date. Enter the first day of your last period and your average cycle length. The calculator adds 280 days (40 weeks) to give your estimated due date. Works best for regular 28-day cycles.

Using Your Conception Date

If you know when you conceived, enter that date instead. The calculator adds 266 days to the conception date to estimate your delivery date. This is useful if your cycle is irregular or if you were tracking ovulation.

IVF Transfer Date Method

For IVF pregnancies, use the embryo transfer date. A Day 3 transfer adds 263 days; a Day 5 transfer adds 261 days. This is the most precise method available.

Understanding Your Estimated Due Date

How Accurate Is a Due Date Calculator?

No, a calculator is 100% accurate, but only about 5% of babies are born on their exact due date. Your doctor will confirm or adjust the date after your first ultrasound, which measures the baby directly and is more precise than any calendar method.

Can My Due Date Change?

Yes. If your cycle is irregular, or if your 12-week ultrasound measurements don't match the LMP calculation, your doctor may revise the date. That's expected.

Your Pregnancy Timeline by Trimester

First Trimester (Weeks 1-12)

The first trimester covers early development, from a fertilized egg to a formed fetus with all major organs taking shape. Most miscarriages, if they happen, occur in this window. Your 12-week scan will be the first time you clearly hear the heartbeat.

Second Trimester (Weeks 13-27)

This is typically the most comfortable stretch. Morning sickness usually eases off, energy returns, and you'll likely feel the baby move for the first time around weeks 18-22. Your anatomy scan happens around week 20.

Third Trimester (Weeks 28-40)

The baby gains most of its weight in these final weeks. You'll have more frequent checkups as you approach your due date. Full term is considered 37-42 weeks.