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Pregnancy due date calculator

Find your estimated due date, see how far along you are and know which trimester you're in. Calculate from your last period, conception date, IVF transfer, ultrasound or current week of pregnancy.

Illustration of a pregnancy due date calculator

Calculate your due date

Last period (most common)

Use the first day of your last period.

First day of last period
September
SunMonTueWedThuFriSat
3031Sep123456789101112131415161718192021222324252627282930Oct12345678910
28 days

Your due date estimate updates automatically as you enter your dates.

Your estimated due date:
Sample
June 16, 2027You're 6 weeks pregnant (about 2 months), with about 34 weeks to go.
1st trimester
2nd trimester
3rd trimester
September 23, 2026Estimated conception
238 daysto go
ZodiacGemini
BirthstonePearl
Chinese zodiacGoat

This is a sample result. Enter your own dates above to calculate your due date.

By Babylist Staff · Medically reviewed by
Dr. Alyssa Dweck
, OB/GYN ·

How far along are you? Find your week, month, and trimester

You're week 6, in your 2nd month, in the 1st trimester.

Weeks Dates Month Trimester Current stage
1–4 Sep 9 – Oct 13, 2026 Month 1 First
5–8 Oct 14 – Nov 10, 2026 Month 2 First You are here
9–13 Nov 11 – Dec 15, 2026 Month 3 First
14–17 Dec 16, 2026 – Jan 12, 2027 Month 4 Second
18–22 Jan 13 – Feb 16, 2027 Month 5 Second
23–27 Feb 17 – Mar 23, 2027 Month 6 Second
28–31 Mar 24 – Apr 20, 2027 Month 7 Third
32–35 Apr 21 – May 18, 2027 Month 8 Third
36–40 May 19 – Jun 16, 2027 Month 9 Third

Calendar dates are based on your estimated due date and update as you change your inputs.

How big is your baby right now?

In weeks 5–8, your baby grows from about the size of a Pop Rocks crystal to a bike spoke bead.

Week 5 — baby is about the size of a Pop Rocks crystal
Week 5Pop Rocks crystal
Week 6 — baby is about the size of a Tiny Chiclet Gum
Week 6Tiny Chiclet Gum
Week 7 — baby is about the size of a Sweethearts candy
Week 7Sweethearts candy
Week 8 — baby is about the size of a bike spoke bead
Week 8bike spoke bead

From Babylist's week-by-week guides

Common questions

How do I use this calculator?

Pick the method that works for you: your last period, conception date, a known due date, IVF transfer, ultrasound date, or how far along you already are. Enter the dates the calculator asks for, and your due date updates automatically.

How is my due date calculated?

Your due date is the first day of your last period plus 280 days, the standard method ACOG uses. Pregnancy is counted in weeks from that day, starting at Week 0 and running to Week 40.[1][2]

How is the date of conception calculated?

Conception is estimated at about two weeks after your last period, around the time you ovulate. Providers date pregnancy from your last period instead of conception because the exact day of conception is hard to know. Implantation alone can happen anywhere from 6 to 12 days after ovulation. Our
implantation guide
 explains the timeline in more detail.[1]

How is a due date estimated from an ultrasound?

An early ultrasound estimates your due date by measuring the baby — the crown-rump length in the first trimester — and comparing it to average growth. ACOG considers a first-trimester scan the most accurate way to date a pregnancy, though even then it carries a margin of about 5 to 7 days.[1]

How is an IVF due date calculated?

With IVF, your due date is counted from the embryo transfer date and the age of the embryo. A day-5 (blastocyst) transfer is dated 261 days out, a day-3 transfer 263 days, and a day-6 transfer 260 days. Because the embryo age is known, IVF dating is very precise — it can differ by a day or two from a general pregnancy app, so follow the dates your fertility clinic gives you.[1]

What if I already know my due date?

Enter it directly to see how far along you are, your trimester, and your estimated conception date. Keep up with your regular prenatal visits, since your provider may adjust the date as your pregnancy progresses.

Can my due date change?

Yes — an early ultrasound can adjust your due date, and the earlier the dating scan, the more accurate the estimate. Longer or irregular cycles also make last-period dating less exact, which is one reason a first-trimester scan is used to confirm.[1]

How likely am I to give birth on my due date?

Due dates are estimates. In a study of natural conceptions, pregnancy length varied by about five weeks (Jukic et al., Human Reproduction, 2013), and the CDC reports about 1 in 10 U.S. births are preterm (before 37 weeks). Most babies arrive within two weeks before or after the due date; twins and multiples usually arrive earlier.[3][6]

How soon can I take a pregnancy test?

Most home pregnancy tests can detect a pregnancy around the day of your missed period, or about one to two weeks after conception. Testing too early can give a false negative, so waiting until your missed period gives a more reliable result. Our
best pregnancy tests guide
 compares the most reliable options.

Why did Babylist make this due date calculator?

We've seen every pregnancy calculator, and they all lacked one thing: a way to count from any path to pregnancy — not just your last period. So we made this one, which estimates your due date six ways and is medically reviewed, to better serve
Babylist Registry
 users. Every year, millions of families use Babylist to feel confident, cared for, and supported from pregnancy through birth and beyond.
Ready to start planning?Now that you know your estimated due date, create a Babylist to plan, prepare and shop for your baby all in one place.
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What month of pregnancy am I in?

Weeks Month
1–4 Month 1
5–8 Month 2
9–13 Month 3
5 weeks
14–17 Month 4
18–22 Month 5
5 weeks
23–27 Month 6
5 weeks
28–31 Month 7
32–35 Month 8
36–40 Month 9
5 weeks

Most months have 4 weeks, but months 3, 5, 6, and 9 have 5. That's why the table doesn't divide evenly. Pregnancy is measured in weeks and trimesters, so these month groupings are an approximation.[1] Quick reference: 12 weeks is about 3 months, 20 weeks is about 5 months, 28 weeks is about 7 months, 36 weeks is about 9 months.

Estimated due date by conception month

Your estimated due date is about 38 weeks (266 days) after the day you conceived.

Last updated October 2026 · Previous 10 months.

If you got pregnant in Estimated due date
September 2026 May 2027
August 2026 April 2027
July 2026 March 2027
June 2026 February 2027
May 2026 January 2027
April 2026 December 2026
March 2026 November 2026
February 2026 October 2026
January 2026 September 2026
December 2025 August 2026

The math behind due date estimates

How your due date is calculated

ACOG dates a pregnancy by adding 280 days (40 weeks) to the first day of your last period — a method called Naegele's rule.[1] Gestational age is counted from that first day, while fetal age starts about two weeks later, at conception.[5]

Trimesters

The first trimester is weeks 1–13, the second is weeks 14–27, and the third is weeks 28–40. ACOG defines full term as 39–40 weeks, early term as 37–38 weeks, late term as 41 weeks, and post-term as 42 weeks or more.[2]

See what to expect in the
first trimester
,
second trimester
,
third trimester
, and
fourth trimester
.

Accuracy

Due dates are estimates. Pregnancy length can vary by about five weeks[6], and the CDC reports about 1 in 10 U.S. births are preterm (before 37 weeks).[3] Most babies arrive within two weeks before or after the due date; twins and multiples usually arrive earlier.

Ultrasound vs. last period — which date is right?

ACOG considers a first-trimester ultrasound the most accurate way to date a pregnancy.[1] If an early dating ultrasound disagrees with your last-period date, your provider re-dates by the ultrasound only when the gap is large enough. Per ACOG Committee Opinion 700:

Gestational age at scan Re-date if the dates differ by
Up to 8 weeks 6 days More than 5 days
9w 0d – 15w 6d More than 7 days
16w 0d – 21w 6d More than 10 days
22w 0d – 27w 6d More than 14 days
28 weeks and beyond More than 21 days

Once an early scan sets your due date, later scans generally shouldn't override it.

Understanding pregnancy dating terms

LMP (last menstrual period)
The first day of your last period. ACOG counts your due date from this day, even though conception happens about two weeks later.[1]
EDD / EDC (estimated due date / estimated date of confinement)
Your baby's estimated arrival, 280 days after your LMP. EDD and EDC mean the same thing.
Gestational age vs. fetal age
Gestational age is counted from your last period; fetal age from conception, about two weeks later. That is why you are "4 weeks pregnant" about two weeks after conception.[5]
DPO (days past ovulation)
Days since you ovulated. Because ovulation is close to conception, N DPO is about N + 14 days of gestational age.

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References

  1. American College of Obstetricians and Gynecologists. Committee Opinion No. 700: Methods for Estimating the Due Date. Obstet Gynecol. 2017;129(5):e150-e154.
    https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date
  2. American College of Obstetricians and Gynecologists; Society for Maternal-Fetal Medicine. Committee Opinion No. 579: Definition of Term Pregnancy. Obstet Gynecol. 2013;122(5):1139-1140.
    https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2013/11/definition-of-term-pregnancy
  3. National Center for Health Statistics. Births: Final Data for 2023 (NCHS Data Brief No. 507). CDC; 2024.
    https://www.cdc.gov/nchs/products/databriefs/db507.htm
  4. National Health Service. Due date calculator. NHS.
    https://www.nhs.uk/pregnancy/finding-out/due-date-calculator/
  5. MedlinePlus. Gestational age. National Library of Medicine.
    https://medlineplus.gov/ency/article/002367.htm
  6. Jukic AMZ, Baird DD, Weinberg CR, McConnaughey DR, Wilcox AJ. Length of human pregnancy and contributors to its natural variation. Hum Reprod. 2013;28(10):2848-2855.
    https://academic.oup.com/humrep/article-abstract/28/10/2848/620772
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