Due Date Calculator

Estimate your baby's due date using different calculation methods.

Select calculation method and enter date(s).

Note: This is an estimate. Your actual delivery date may vary. Ultrasound dating by a healthcare provider is generally more accurate, especially if your cycles are irregular.

Estimating Your Baby's Arrival: The Due Date Calculator

Finding out you're pregnant is an exciting time, and one of the first questions that comes to mind is: "When is the baby due?" An estimated due date (EDD) helps you, your family, and your healthcare provider plan for the baby's arrival. Our Due Date Calculator offers several common methods to estimate this important date.

How to Use the Due Date Calculator

  1. Select Calculation Method: Choose how you want to calculate the due date:
    • Last Period (LMP): This is the most common method. Select this and enter the first day of your last menstrual period and your average cycle length (default is 28 days).
    • Conception Date: If you know the approximate date of conception (often close to ovulation), select this and enter the date.
    • IVF Transfer: For IVF pregnancies, select this option, enter the date of the embryo transfer, and specify whether it was a 3-day embryo or a 5-day blastocyst transfer.
  2. Enter Date(s): Provide the required date(s) based on your chosen method.
  3. Click Calculate: Press the button.

The calculator will display your estimated due date and often the current estimated gestational age (how many weeks and days pregnant you are).

Common Due Date Calculation Methods

  • Naegele's Rule (Based on LMP): This standard method assumes a 28-day cycle with ovulation on day 14. It calculates the EDD by adding 280 days (40 weeks) to the first day of the LMP. Adjustments are sometimes made for cycle lengths different from 28 days, although this calculator applies the standard 280 days.
  • Conception Date: If the conception date is known, the EDD is typically calculated by adding 266 days (38 weeks – the average length of gestation from conception) to that date.
  • IVF Transfer Date: For IVF, the calculation is more precise based on the age of the embryo at transfer.
    • 3-Day Transfer: EDD = Transfer Date + 266 days - 3 days
    • 5-Day Transfer: EDD = Transfer Date + 266 days - 5 days

Why is the Due Date an Estimate?

It's important to remember that the EDD is just an estimate. Only about 4-5% of babies are born exactly on their due date. Several factors influence the actual delivery date:

  • Irregular Cycles: If your menstrual cycles aren't consistently 28 days, LMP-based calculations can be less accurate.
  • Ovulation Timing: Ovulation doesn't always occur exactly 14 days before the next period.
  • Individual Variation: Each pregnancy and baby develops at a slightly different pace.
  • First vs. Subsequent Pregnancies: First babies are slightly more likely to arrive after the due date.

Ultrasound dating, especially when performed early in the first trimester (measuring the baby's crown-rump length), is generally considered the most accurate method for determining gestational age and refining the EDD.

Using Your Estimated Due Date

Your EDD is a helpful guide for:

  • Tracking pregnancy milestones.
  • Scheduling prenatal appointments and tests.
  • Planning maternity leave and preparing for the baby's arrival.
  • Giving your healthcare provider a baseline for monitoring fetal growth.

Use our calculator to get a good initial estimate, but always confirm your due date and discuss your pregnancy timeline with your doctor or midwife.