Twin due date calculator
See a standard due date and the common early-arrival window in one step.
Direct answer: the standard estimate is still 280 days from your last period, but many uncomplicated twin pregnancies deliver around weeks 36–37—so this calculator shows both.
Twin pregnancies are conventionally dated the same way as singleton pregnancies—280 days from your last period—but many twins arrive earlier. Your care team will re-date from an early ultrasound, which is more reliable than an LMP estimate.
Choose the first day of your last period to begin.
Two numbers worth knowing
The conventional 40-week due date gives you a planning anchor, and the earlier window reflects how twin pregnancies actually tend to unfold. Neither is a guarantee—delivery timing depends heavily on chorionicity, growth and your individual care plan.
Once your dates are confirmed by ultrasound, our hospital bag checklist is worth starting earlier than usual, since twins are more likely to arrive ahead of a standard due date.
Common questions
Is a twin due date calculated differently from a singleton?
The standard 280-day, 40-week estimate from the last menstrual period is the same starting point. What differs is that twin pregnancies more often deliver before that date, so many clinicians treat 40 weeks as a ceiling rather than a target.
When do twins usually arrive?
Many uncomplicated twin pregnancies deliver around 36 to 37 weeks, though timing varies by chorionicity (whether twins share a placenta) and individual health factors. Your care team will set a personalized plan.
Is LMP dating reliable for twin pregnancies?
An early first-trimester ultrasound is generally considered more reliable than LMP-based dating for any pregnancy, and it's especially useful for twins to help establish chorionicity and confirm dating early.
Does carrying twins change my due date, or just delivery timing?
The calculated due date itself uses the same method. What changes in practice is that many care teams plan delivery earlier than 40 weeks for twin pregnancies, based on chorionicity and how the pregnancy is progressing.
More tools for your timeline
Conceived through IVF? Try the IVF due date calculator, or use the hospital bag checklist to get ready early.