Free, private & instant

Pregnancy Due Date Calculator

Estimate your baby's due date from the first day of your last period, a known conception date, or an IVF transfer. See your pregnancy week, trimester, and milestone timeline in seconds.

Choose how to calculate

Use the date you know best.

Use the first day of bleeding, not the day it ended.

The standard estimate assumes a 28-day cycle.

Your dates stay in your browser.

Your pregnancy journey starts here Choose a method and enter one date to reveal your estimated due date and milestone timeline.
Your estimated due date
January 1, 2027

Pregnancy progress today
Estimated arrival window
Your 40-week journey
Week 0Week 13Week 27Week 40
Second trimester
Third trimester
37 weeks

An estimate, not a diagnosisYour clinician or midwife may confirm or revise dating using your history and an early ultrasound. Follow their due date for your care.

Multiple dating methods

Calculate from your last period, cycle length, conception date, or a day-3 or day-5 IVF transfer.

Your journey at a glance

See your pregnancy week, trimester, estimated arrival window, and key calendar milestones together.

Private by design

Your dates are calculated locally. The calculator does not upload or store the personal dates you enter.

How to use the pregnancy due date calculator

This free pregnancy due date calculator online gives you an estimated due date (EDD) and a simple timeline. Start with the dating method for which you have the most reliable information.

  1. Choose a methodSelect last period, conception, or IVF transfer. Last period is the most common starting point.
  2. Enter your dateAdd the requested date. If using your last period, adjust the usual cycle length if it differs from 28 days.
  3. Explore your timelineView the estimated due date, pregnancy week, trimester, arrival window, and milestone dates.

How is a pregnancy due date calculated?

Pregnancy dating uses gestational age, which is conventionally counted from the first day of the last menstrual period rather than from conception. That is why a 40-week pregnancy is approximately 38 weeks from conception. An online result is useful for planning, but it remains an estimate.

From the last menstrual period

The standard calculation adds 280 days, or 40 weeks, to the first day of your last period. The cycle-length setting shifts this estimate earlier or later when your usual cycle is shorter or longer than 28 days.

Due date = LMP + 280 days + (cycle length - 28)

From conception

If conception or ovulation is known with reasonable confidence, the calculator adds 266 days. Ovulation can vary even in regular cycles, so an estimated conception date may still produce an approximate result.

Due date = conception date + 266 days

From an IVF transfer

IVF dating accounts for the embryo's age on transfer day. A day-3 embryo transfer uses 263 days after transfer; a day-5 transfer uses 261 days after transfer.

Day 3: +263 days  |  Day 5: +261 days

Why the date can change

Uncertain period dates, irregular cycles, and variation in ovulation can affect calendar dating. A clinician can compare this estimate with an early ultrasound and your medical history to establish the date used for care.

Health information sources: The 280-day convention and IVF dating formulas follow the American College of Obstetricians and Gynecologists. The general 37-to-42-week pregnancy range and cycle-length adjustment are consistent with the NHS pregnancy due date guidance. This page is educational and is not a substitute for medical care.

What your estimated due date means

Your EDD is a reference point for tracking gestational age and planning care; it is not a promise that labor will begin on that exact day. Pregnancy commonly spans roughly 37 to 42 weeks from the first day of the last period. Your personal care team may use an early ultrasound or known assisted-reproduction dates to confirm the best obstetric estimate.

Pregnancy week and day

The result shows completed gestational weeks and days as of today. For example, 12 weeks and 3 days means 12 full weeks have passed and you are in your 13th week.

Trimester timeline

This tool uses week 13 as the beginning of the second trimester and week 27 as the beginning of the third. Clinical conventions can vary slightly, so follow the labels used by your care team.

Estimated arrival window

The displayed 37-to-42-week window helps show why the due date is only one point on a broader timeline. It should not be used to make medical decisions about delivery timing.

When dates are uncertain

If you do not know the first day of your last period, your cycles are irregular, or different dating methods disagree, speak with a midwife, obstetrician, or other qualified clinician.

Pregnancy due date calculator FAQ

Answers to common questions about estimated due dates, pregnancy weeks, cycle length, IVF dating, and privacy.

How is a pregnancy due date calculated?

The most common estimate adds 280 days, or 40 weeks, to the first day of the last menstrual period. A known conception date uses 266 days. IVF transfer calculations account for embryo age.

How accurate is an online due date calculator?

It gives an estimate, not a guaranteed delivery date. Recall of the last period, cycle irregularity, and the timing of ovulation can affect the result. A clinician may establish or confirm dating with an early ultrasound.

What if my cycle is longer or shorter than 28 days?

Select your usual cycle length. The calculator adjusts the last-period estimate by the number of days above or below 28. If cycles vary significantly, ask a healthcare professional which dating method to use.

Can I calculate a pregnancy due date after IVF?

Yes. Enter the transfer date and choose a day-3 or day-5 embryo. The tool adds 263 days for a day-3 transfer or 261 days for a day-5 transfer, following standard assisted-reproduction dating conventions.

Why does pregnancy start before conception?

Gestational age is conventionally counted from the first day of the last period. In a typical 28-day cycle, this is about two weeks before ovulation and conception.

Does this calculator save my dates?

No. The dates are processed locally in your browser and are not uploaded or stored by this calculator. Standard site analytics are configured without the dates or due-date result.

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