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Due Date Calculator

Estimate your baby's due date from your last period, conception date, IVF transfer or an ultrasound, with trimester dates.

Formulas last reviewed: September 2026

Disclaimer: Results are general estimates for information and education only. They are not medical advice, a diagnosis or a treatment plan. Please talk to a doctor or qualified health professional before making health, diet, exercise or pregnancy decisions.

What is an estimated due date?

Your estimated due date (EDD) is when you reach 40 weeks of pregnancy. It helps you and your doctor plan scans, tests and delivery.

It can be worked out from several starting points: the first day of your last period, the conception date, an IVF embryo transfer or a dating ultrasound. All of them should land on almost the same date.

How it is calculated

From last period: LMP + 280 days (adjusted if your cycle is not 28 days)
From conception: + 266 days · IVF: transfer + 261 (day 5) or 263 (day 3)

Ultrasound: the due date is the scan date plus the days remaining until 40 weeks.

Worked example

Different methods, same pregnancy

Last period 1 Jan 2026
Thu, 8 Oct 2026
Conception 15 Jan 2026
Thu, 8 Oct 2026
Day-5 transfer 20 Jan 2026
Thu, 8 Oct 2026
Scan 12 Mar 2026 at 10w0d
Thu, 8 Oct 2026

How reliable is a due date?

  • Only about 4–5% of babies are born on the exact date; most arrive between 37 and 42 weeks.
  • A first-trimester ultrasound is the most accurate way to date a pregnancy.
  • A longer cycle pushes the due date later, a shorter cycle earlier.
  • First babies and twins are more likely to come at different times than average.

Frequently asked questions

Will my baby really arrive on my due date?

Very few do. Think of the due date as the middle of a window. Full term is 37 to 42 weeks.

Why did my doctor change my due date?

If an early scan measures the baby differently from your last-period date by more than about a week, doctors often use the scan date.

How is the due date calculated with a 32-day cycle?

Add the difference from 28 days. A 32-day cycle moves the date 4 days later than the standard LMP + 280 days.

What does “term” mean?

Early term is 37–38 weeks, full term 39–40 weeks, late term 41 weeks and post-term 42 weeks and beyond.