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Pregnancy Due Date Calculator

Estimate your baby's due date and see your pregnancy timeline.

days

Most cycles are 21 to 35 days. Use 28 if you are not sure.

Choose a date

Your due date and pregnancy timeline appear here.

Results are estimates for general information only and are not medical advice. Talk to a doctor or other qualified health professional about your health. Read our disclaimer.

When to use it

The pregnancy due date calculator estimates when your baby is due and shows a simple timeline of key milestones: the likely conception date, when a test could turn positive, the end of the first trimester, the anatomy scan window, the start of the third trimester and full term. Use it after a positive test to plan appointments, work leave and conversations with family, and to understand how far along you are.

How to calculate your due date

  1. Under Calculate based on, choose:
    • First day of last period (the most common method).
    • Conception date, if you know it.
    • IVF: 5-day embryo transfer or IVF: 3-day embryo transfer.
  2. Enter the date asked for.
  3. For the period method, set your Average cycle length (most cycles are 21 to 35 days; use 28 if you’re not sure).
  4. Read the Estimated due date, how many days are left and how many weeks pregnant you are today.
  5. Check the timeline below for each milestone.

A worked example

Your last period started on 1 March 2026 and your cycles are usually 28 days. The calculator adds 280 days (40 weeks) and gives an estimated due date of Sunday, 6 December 2026. The timeline shows conception around 15 March, a positive test possible from about 29 March, the end of the first trimester on 6 June, and full term (39 weeks) from 29 November. If your cycles are usually 32 days, the due date moves to 10 December.

How the dates are worked out

The standard method, called Naegele’s rule, adds 280 days to the first day of the last period, assuming a 28-day cycle with ovulation on day 14. For other cycle lengths, the date shifts by the difference. From a conception date the calculator adds 266 days, and for IVF it counts back from the embryo’s known age at transfer.

Tips

  • Write down period start dates each month; it makes the estimate more reliable.
  • Book an early scan if your cycles are irregular or you’re unsure of the date.
  • Plan around a window, not a single day. Most babies come between 37 and 42 weeks.
  • Share the timeline with your partner or family so everyone knows the milestones.

Common mistakes

  • Using the last day of the period instead of the first.
  • Ignoring cycle length. A long cycle can move the due date by a week or more.
  • Treating weeks as months. Pregnancy is about 40 weeks, a little over nine months.
  • Replacing medical advice. Your midwife or doctor’s dating scan takes priority.

Track fertile days with the Ovulation Calculator, count the days until the big day with the Countdown Timer, or check your daily water needs with the Water Intake Calculator.

Frequently asked questions

How accurate is a due date?

It's an estimate. Only about 1 in 25 babies arrives on the exact due date; most are born within two weeks either side. An early ultrasound scan usually gives the most accurate date, and your care team may adjust it.

Why is pregnancy counted from my last period, not conception?

Most people know when their last period started but not exactly when they conceived. Counting from the period adds about two weeks, which is why you are "2 weeks pregnant" around conception.

What if my cycle isn't 28 days?

Enter your usual cycle length. Longer cycles mean ovulation happens later, so the due date moves later by the same number of days; a 32-day cycle adds 4 days.

How do I calculate the date after IVF?

Choose "IVF: 5-day embryo transfer" or "IVF: 3-day embryo transfer" and enter the transfer date. Because the embryo's age is known exactly, IVF due dates are the most precise.

Is my information stored?

No. Dates are calculated in your browser and nothing is saved or sent.

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