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Pregnancy Calculator

Estimate your due date and track how far along you are from your last period, conception date, ultrasound, IVF transfer, or a known due date — with conception date, trimester, and key milestone dates.

days

Days from the start of one period to the next (default 28).

Estimated due date

Third trimester

October 8, 2026

You are
34 weeks 4 days pregnant
Estimated conception date
January 15, 2026
Time to due date
5 weeks 3 days to go

Key dates

MilestoneDate
Estimated conceptionJanuary 15, 2026
End of first trimester (week 13)April 8, 2026
End of second trimester (week 27)July 15, 2026
Full term begins (week 37)September 17, 2026
Estimated due date (week 40)October 8, 2026
Estimated due dateOctober 8, 2026View results

Enter the information you have — your last period, a known due date, the conception or IVF transfer date, or an ultrasound measurement — and this calculator estimates your due date, how far along you are today, your trimester, and the key milestone dates of your pregnancy.

Formula

Every method is reduced to a single estimated due date (EDD), and everything else is measured from it:

Last period:  EDD = last period + 280 days + (cycle length - 28)
Conception:   EDD = conception date + 266 days
Ultrasound:   EDD = scan date + (280 - gestational age at scan)
IVF transfer: EDD = transfer date + 266 - embryo age (e.g. 261 for day 5)
Due date:     EDD is entered directly

Gestational age "today" is the days between today and the last-period date (or its equivalent), expressed as weeks and days.

A pregnancy is dated from the last menstrual period, so you are considered about 2 weeks "pregnant" at conception. That's why the count is 40 weeks from your period but 38 weeks from conception.

Pregnancy milestones

MilestoneGestational age
End of first trimesterWeek 13
End of second trimesterWeek 27
Full term beginsWeek 37
Estimated due dateWeek 40
Post-termAfter week 42

Examples

Last period on January 1, 2024 (28-day cycle)

EDD = January 1 + 280 days = October 7, 2024, with an estimated conception date of January 15, 2024. As of March 15, 2024 you would be 10 weeks 4 days along — in the first trimester.

Day-5 IVF transfer on January 1, 2024

EDD = transfer + 261 days = September 18, 2024.

Frequently asked questions

How is a due date calculated?
The most common method is Naegele's rule — add 280 days (40 weeks) to the first day of your last menstrual period. Because ovulation and conception happen about two weeks after that, a pregnancy is roughly 38 weeks from conception but 40 weeks from the last period.
How accurate is an estimated due date?
It's an estimate, not a guarantee. Fewer than 4% of babies arrive exactly on the due date, about 60% within a week of it, and nearly 90% within two weeks. An early ultrasound is generally the most accurate way to date a pregnancy.
What if my cycle isn't 28 days?
The last-period method assumes ovulation around day 14. If your cycle is longer or shorter, ovulation shifts accordingly, so this calculator adjusts the due date by the difference between your cycle length and 28 days.
How does the IVF option work?
With IVF the conception date is known precisely, so the due date is the transfer date plus 266 days minus the embryo's age. A day-5 (blastocyst) transfer adds 261 days; a day-3 transfer adds 263 days.
What counts as full term?
The World Health Organization considers 37 to 42 weeks a normal-length pregnancy. Before 37 weeks is preterm; after 42 weeks is post-term. The milestone table shows the dates these windows begin for your pregnancy.

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