Wondering when your twins or triplets are due? Enter your details to get an instant 40-week EDD and the typical delivery window for multiples (based on the dating method you choose). Curious about odds? See the chance of twins for your age and history.
Twin & Triplet Due Date Calculator
Delivery window calendar
Green marks your delivery planning estimate, pink shows the delivery window, and the outlined date is your 40-week due date. A pink arrow means highlighted dates are in that direction.
Planning estimate Delivery window 40-week due date
Methodology & sources
The green date is a planning reference, not the most likely day of spontaneous birth. With twin type unknown, it marks 37 weeks, the most common completed birth week in a US birth-certificate study. The data do not identify a most likely day within that week.
For known types, the reference follows delivery guidance: di/di twins at 38 weeks (NICHD/SMFM workshop), mono/di at 36 weeks and eligible uncomplicated triplets at 35 weeks (NICE). The mono/mono reference is 33 weeks, a planning point within the 32-34-week guidance range, not a measured peak. Recommendations vary by country and clinical circumstances. Many births happen before planned delivery; a different triplet placental or sac arrangement needs individual advice.
EDD dating: 280 days (40 weeks) from LMP (Naegele’s rule); or by early ultrasound (EDD = scan date + (280 days − measured GA)); or for IVF/FET by adding ~263 days (day-3), 261 days (day-5), or 260 days (day-6) to the transfer date.
Multiples timing (uncomplicated): di/di ≈ ~38w; mono/di ≈ ~36–37w; mono/mono ≈ ~32–34w; triplets ≈ ~35–36w. Final timing is individualized by your care team.
See How it works and Data sources for citations.
For a simple singleton due date from your last period or ultrasound, use the Pregnancy Due Date Calculator.