Twin & Triplet Due Date Calculator

Updated Aug 2025 · Written by

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).

Twin & Triplet Due Date Calculator

If unsure, leave as “I’m not sure”.
EDD: —
Gestational age today: —
Typical delivery window (uncomplicated):
—
Methodology & sources

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.

Frequently asked questions

How accurate is the twins/triplets due date?
EDD is a 40-week baseline. Multiples often deliver earlier; timing is individualized by your care team.
What if I conceived via IVF/FET?
EDD can be calculated from transfer date and embryo day (3/5/6). Your clinic may confirm/adjust with early ultrasound.
What is chorionicity and why does it matter?
It describes how twins share a placenta and sacs (di/di, mono/di, mono/mono). It guides typical delivery windows.
Should I use LMP or ultrasound to date the pregnancy?
Use your most reliable method. Early ultrasound commonly replaces LMP if they differ meaningfully.