Due Date Calculator for Twins & Multiples
Estimate a twin or multiples due date, with the typical earlier-arrival window.
Twin due date plus typical arrival window — free, privateEstimates only — not medical advice. Confirm all dates and milestones with your doctor or midwife. Read our full disclaimer.
How this due date is calculated
Enter the first day of your last period. The official estimated due date uses LMP + 280 days. Because twins often arrive early, the typical arrival is closer to LMP + 259 days (about 37 weeks) — treat that as an average, not your personal due date.
Multiples do not change the math of the due date, but they sharply change the delivery window. A twin pregnancy is biologically driven to deliver earlier — partly because the uterus hits its stretching threshold sooner with two occupants — so the average twin birth lands near 37 weeks. That is why this page shows both the standard estimated due date and a separate "typical arrival" figure, which is a planning hint rather than your personal date.
What to expect
For twins and other multiples, the official estimated due date still starts from the last period using the standard 280-day rule. Multiples do not change the due-date formula — but they do change when babies tend to actually arrive.
Twins and triplets are usually born early. On average, twins arrive around 37 weeks (about LMP + 259 days) rather than the full 40. Triplets often arrive even earlier. That is why the result above shows both the standard estimated due date and an "average arrival" date — the second is a planning hint, not a medical promise.
Example: an LMP of January 1 gives a standard due date near October 8, with an average twin arrival nearer September 27. Your provider will set a personalized schedule and may recommend earlier monitoring as the pregnancy progresses.
Because early arrival is common with multiples, many parents find it useful to have bags packed and appointments scheduled a few weeks ahead of the standard date. Treat the average-arrival date as a gentle nudge, not a guarantee.
As with any pregnancy, an early ultrasound is the most reliable way to confirm dating, especially when cycles are irregular.
Important note
These calculators use standard formulas — Naegele's rule (LMP + 280 days) and common IVF conventions (transfer date + 260–263 days). They give estimates for planning only. They are not a substitute for prenatal care, and only your provider can confirm your due date and track your baby's development. See the disclaimer for details.
FAQ
How is a twins due date different?
The official estimated due date still uses LMP + 280 days, but twins usually arrive early — often around 37 weeks. The calculator shows both the standard date and a typical earlier arrival as a planning hint.