Pregnancy timeline and due date estimate

Pregnancy Due Date Calculator

Estimate your due date, current pregnancy week and trimester from the information you know, with a clear 40-week timeline and estimated birth window.

Estimate your pregnancy timeline

Choose the dating method that matches the information available to you.

Your estimated pregnancy timeline

Estimated due date–

Based on: –

Gestational age today–

Current stage–

Time to estimated due date–

Based on–

Progress through 40 weeks

The marker shows the estimated gestational age today.

010203040 weeks

Estimated birth window

Pregnancy commonly lasts from 37 to 42 weeks from the first day of the last menstrual period. The dates below are a planning range, not a prediction of the birth day.

37 weeks–

Estimated due date–

42 weeks–

This calculator provides an educational estimate and cannot replace dating by a midwife, obstetrician or other qualified clinician.

Pregnancy milestone timeline

Dates are calculated from the estimated start of gestational age. Medical appointments and tests follow your local care plan.

Save the estimate

Add due date to calendar

Download the estimated due date as a private calendar event or print the result. The entered dates stay in your browser.

Private calculation

The calculation and calendar file are created in your browser. This tool does not need to store the dates you enter.

How pregnancy dating works

Last menstrual period

The standard estimate is 280 days from the first day of the last menstrual period. The cycle-length adjustment accounts for cycles that differ from 28 days.

Ultrasound dating

An early ultrasound can establish or confirm gestational age. Later ultrasound dating has a wider margin of uncertainty, so clinical interpretation matters.

IVF embryo transfer

For IVF, the estimate uses the transfer date and embryo age: 263 days after a day-3 transfer or 261 days after a day-5 transfer.

Private calculation

The calculation and calendar file are created in your browser. This tool does not need to store the dates you enter.

Medical context and sources

The formulas and explanatory ranges follow guidance from ACOG guidance on estimating the due date and NHS pregnancy due date guidance. Your healthcare professional should confirm the official due date used in your care.

Pregnancy Due Date Calculator FAQ

Is the estimated due date the exact birth date?

No. It is a planning estimate. Pregnancy commonly lasts between 37 and 42 weeks, and only a small proportion of babies arrive on the estimated due date.

Why are pregnancy weeks counted from the last period?

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

Which method should I use?

Use the most reliable information available. A clinician may compare the last period with an early ultrasound and document the best obstetric estimate.

How does cycle length change the result?

For the LMP method, the estimate shifts by the difference between your usual cycle length and 28 days.

Can the calculator handle IVF?

Yes. Select IVF embryo transfer and choose whether a day-3 or day-5 embryo was transferred.

Does this calculator provide medical advice?

No. It is an educational planning tool. Discuss pregnancy dating, symptoms and care decisions with a qualified healthcare professional.