Twin due date calculator
See your due date for twins and the window when delivery is usually planned, based on the type of twins you’re carrying. Everything runs in your browser; nothing is saved or sent.
The first day of bleeding.
Default 28.
From your scan or IVF clinic.
Usually found on an early scan.
How to use it
- Enter your last period or your due date. If an early scan or IVF clinic gave you a due date, use that: it’s usually more accurate than the last period.
- Choose the type of twins. Di-di, mo-di or mo-mo, from your scan report. If you don’t know yet, leave “Not sure yet” and you’ll see all three.
- Read the dates. You’ll get your standard 40-week due date, the usual planned delivery window as calendar dates, how far along you are today, and key dates such as 32, 34 and 37 weeks.
Why twins usually arrive early
A twin pregnancy is calculated from the same starting point as any other: 40 weeks from the first day of the last period, or from an early ultrasound or IVF date. But twins rarely go that long. More than half are born before 37 weeks, and even when everything is going smoothly, clinicians usually plan delivery earlier than for a single baby, because the risks of continuing past a certain point start to outweigh the benefits.
Planned delivery timing by type of twins
For uncomplicated twin pregnancies, ACOG and the Society for Maternal-Fetal Medicine suggest these windows:
| Type of twins | What it means | Planned delivery (weeks) |
|---|---|---|
| Dichorionic-diamniotic (di-di) | Two placentas, two sacs | 38 0/7 – 38 6/7 |
| Monochorionic-diamniotic (mo-di) | Shared placenta, two sacs | 34 0/7 – 37 6/7 |
| Monochorionic-monoamniotic (mo-mo) | Shared placenta and sac | 32 0/7 – 34 0/7 |
These are starting points for uncomplicated pregnancies. Growth differences between the babies, conditions such as twin-to-twin transfusion syndrome, high blood pressure or other complications can bring the date forward, and your care team will set the plan for you.
Chances of having twins
In the United States, the twin birth rate was 30.1 per 1,000 births in 2024, down from a peak of 33.9 in 2014 (CDC). Fraternal twins are more likely with fertility treatment such as IVF, in your 30s, with fraternal twins in the family, after previous pregnancies, and with a BMI of 30 or more. Identical twins happen at a fairly steady rate and aren’t thought to run in families. A higher hCG level can hint at twins but can’t confirm them; only an ultrasound can.
After the birth
If your twins arrive before 37 weeks, their development is usually tracked by corrected age — their age counted from the due date — for the first couple of years.
Frequently asked questions
Is the due date different for twins?
The due date itself is worked out the same way — 40 weeks from the last period, or from an ultrasound or IVF date. What differs is timing: twins are usually born earlier, and clinicians often plan delivery before 40 weeks. The calculator shows both the standard due date and the usual planned window.
When are twins usually born?
More than half of twins are born before 37 weeks, according to March of Dimes. For uncomplicated twins, ACOG and SMFM guidance suggests planning delivery at 38 weeks for dichorionic-diamniotic twins, between 34 and 37 6/7 weeks for monochorionic-diamniotic twins, and between 32 and 34 weeks for monoamniotic twins.
What do di-di, mo-di and mo-mo mean?
They describe whether the twins share a placenta (chorion) and an amniotic sac. Di-di twins have two placentas and two sacs; mo-di twins share one placenta but have two sacs; mo-mo twins share both. It’s usually identified on an early ultrasound and it shapes how the pregnancy is monitored and when delivery is planned.
What are the chances of having twins?
In the United States there were about 30 twin births per 1,000 births in 2024 (CDC). The chances are higher with fertility treatment such as IVF, in your 30s, with fraternal twins in the family, after previous pregnancies, with a BMI of 30 or more, and among Black mothers. Identical twins happen at a roughly similar rate everywhere and aren’t inherited.
Can hCG show I’m having twins?
Not reliably. hCG is higher on average with twins, but the ranges overlap a lot with single pregnancies. Only an ultrasound can confirm twins.
Sources
- StatPearls (NCBI Bookshelf) — Multiple Birth Delivery (citing ACOG Committee Opinion 831 and SMFM)
- ACOG — Medically Indicated Late-Preterm and Early-Term Deliveries (Committee Opinion 831)
- CDC NCHS — A Decade of Decline in Twin Childbearing in the United States, 2014–2024
- March of Dimes — Being pregnant with twins, triplets and other multiples
Last meaningfully updated: 2026-10-14.