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Pregnancy Calculator

Estimate a due date and see the week-by-week pregnancy timeline.

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Milestones

MilestoneWeekDate

Estimated due date

—

How far along—
Trimester—
Days remaining—
Estimated conception—
Full-term window—

Progress

An estimate for planning, not medical advice. Only about four percent of babies arrive on the estimated date, and an early ultrasound dates a pregnancy more accurately than any calculation. Follow the date your midwife or doctor gives you.

Quick Tool Overview

The Pregnancy Calculator estimates a due date from the first day of the last menstrual period, a known conception date or an IVF transfer date, and shows how far along the pregnancy is and which trimester that falls in.

What it does
Estimates a due date and maps the pregnancy timeline
You give it
A last period, conception or IVF transfer date
You get back
The estimated due date, current week and trimester
Best for
Planning ahead between appointments and scans
Calculators Free, unlimited use No sign-up Runs in your browser

About the Pregnancy Calculator

Estimate a due date from the first day of the last menstrual period, a known conception date, or an IVF transfer date. The calculator returns the estimated due date, how far along the pregnancy currently is, and which trimester that falls in.

The standard method is Naegele's rule: add 280 days to the first day of the last period, which assumes a 28-day cycle with ovulation on day 14. Cycle length can be adjusted, since a longer or shorter cycle shifts the date accordingly. Remember that only about four percent of babies arrive on the estimated date; anything from 37 to 42 weeks is full term, and a dating scan is more accurate than any calculation.

Key features of the Pregnancy Calculator

Three starting points

Last menstrual period, known conception date or IVF transfer date, since not everyone has the same information.

Naegele's rule

The standard method — 280 days from the first day of the last period — stated openly rather than hidden.

Cycle length adjustable

The default assumes a 28-day cycle with ovulation on day 14; a longer or shorter cycle shifts the date accordingly.

Week-by-week timeline

Where you are now and what comes next, laid out across the trimesters.

Realistic about the date

Only about four percent of babies arrive on the estimated date, anything from 37 to 42 weeks is full term, and a dating scan is more accurate than any calculation.

How to use the Pregnancy Calculator

  1. 1

    Choose your starting point

    Use the first day of your last period, a known conception date, or an IVF transfer date.

  2. 2

    Adjust your cycle length

    The default is 28 days. Setting your own cycle length shifts the estimate to match.

  3. 3

    Read the timeline

    You get the estimated due date, current gestational age, trimester dates and key milestones.

Frequently asked questions

By Naegele's rule: 280 days, or 40 weeks, from the first day of the last menstrual period. That assumes a 28-day cycle, so the calculator adjusts if yours differs.

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