Pregnancy due date calculator
Find your estimated due date, how far along you are today and the key dates ahead, from your last period, conception, an IVF transfer or an ultrasound.
Sealed on this device
Runs in your browser. Nothing is uploaded.
Sealed
Calculate from
From the first day of one period to the first day of the next. Keep 28 if you’re not sure.
Only if you know it, for example from ovulation tests. Otherwise, use your last period.
Your dates
Estimated due date
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Enter a date to see your due date.
How far along today
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- Since conception
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- Likely conception
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Weeks are counted from the first day of the last period, as midwives and doctors do. Conception usually happens about two weeks later, so the time since conception is about two weeks shorter. Some countries, such as France, use both counts: check which one a document means.
Key dates
Usual windows. Your care team gives you your own appointments.
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Today
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First-trimester scan and screening
An ultrasound before 14 weeks, such as this one, is the most accurate way to date a pregnancy.
11+0 to 13+6
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Second trimester begins
14+0
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Mid-pregnancy anatomy scan
Usually between 18 and 22 weeks, to look at how the baby is growing and developing.
18+0 to 22+6
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Third trimester begins
28+0
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Early term
From 37+0, a baby is no longer considered preterm.
37+0 to 38+6
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Full term
39+0 to 40+6
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Estimated due date
Few babies arrive on this exact day: most are born in the weeks around it.
40+0
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Late term
41+0 to 41+6
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Post-term
from 42+0
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This is an estimate. Your midwife or doctor sets the official dates, usually from your first ultrasound.
Due date methods: ACOG Committee Opinion 700. Terms: ACOG Committee Opinion 579. Preterm birth: WHO.
How it works
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Choose how to calculate
Your last period is the usual starting point. If you know the conception date, had an IVF transfer or have an ultrasound result, choose that instead.
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Enter the date
Add your cycle length, the embryo’s age or the age measured at the scan when asked. The results appear as soon as the date is complete.
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Read your dates
See your estimated due date, how far along you are today, your trimester and the key dates ahead, then copy them if you like.
Frequently asked questions
How is the due date calculated?
From the first day of your last period, the calculator adds 280 days, or 40 weeks: this is Naegele’s rule. From a conception date, it adds 266 days. After IVF, it counts from the transfer date: 263 days for a day-3 embryo and 261 days for a day-5 embryo. From an ultrasound, it starts from the age measured that day. The last-period, IVF and ultrasound methods are those described by the American College of Obstetricians and Gynecologists (ACOG Committee Opinion 700, “Methods for Estimating the Due Date”).
Why does my cycle length change the due date?
Naegele’s rule assumes a 28-day cycle, with ovulation around day 14. Ovulation usually happens about 14 days before the next period, so in a longer cycle it comes later, and the due date moves by the same number of days. With a 35-day cycle, the date is 7 days later than with a 28-day cycle; with a 21-day cycle, 7 days earlier. If your cycles vary a lot, an early ultrasound gives a more reliable date.
What’s the difference between weeks of pregnancy and weeks since conception?
Midwives and doctors count a pregnancy from the first day of the last period. This is the gestational age, written in weeks and days: 24+3 means 24 weeks and 3 days. Conception usually happens about two weeks after that day, so the time since conception is about two weeks shorter, 22 weeks and 3 days in this example. Some countries, such as France, use both counts in everyday life, under different names. Check which one a document or an appointment refers to.
When do the trimesters start, and what do “early term” and “full term” mean?
The calculator uses a common convention: the second trimester starts at 14+0 and the third at 28+0. Some countries and leaflets draw the lines a week or two differently. For birth, ACOG defines early term as 37+0 to 38+6, full term as 39+0 to 40+6, late term as 41+0 to 41+6 and post-term as 42+0 onwards (Committee Opinion 579, “Definition of Term Pregnancy”). The World Health Organization (WHO) calls a birth before 37 weeks preterm.
Will my baby be born on the due date?
Probably not on that exact day: few babies are. The due date marks 40 weeks, and most babies are born in the weeks around it. It mainly helps to plan check-ups and scans. Your midwife or doctor sets the official dates, usually from your first ultrasound: ACOG considers an ultrasound before 14 weeks the most accurate way to date a pregnancy, and WHO recommends one ultrasound before 24 weeks.
Is what I enter saved?
No. The calculation runs in your browser. Your dates are never sent anywhere and nothing is saved, not even on this device: close the page and they’re gone.