Twin Due Date Calculator
Enter the first day of your last period or a due date your provider gave you. We'll show your full-term estimated due date, how far along you are today, and the window when twins most often arrive — all in your browser, nothing saved or sent.
Calculate your dates
Based on a typical 28-day cycle. Your provider may adjust this after an ultrasound.
Use the 40-week due date your OB or midwife gave you.
Your results
Pick a date above to see your estimated due date, how far along you are, and the typical twin arrival window.
Why twins usually arrive earlier
A single-baby pregnancy is dated to 40 weeks, and that 40-week date is still the reference point for twins. But twins rarely stay that long. On average, twins arrive around 35 to 37 weeks, and many providers plan delivery somewhere in the 34–37 week range to keep both babies safe.
Your twin type matters
Di/di twins (two placentas, two sacs) often go closer to 37–38 weeks, while mono/di and mono/mono twins are usually delivered earlier because they need closer monitoring. This tool shows a general, informational window — your care team sets your actual delivery plan based on your pregnancy, scans, and health.
Informational only — not medical advice. This calculator gives rough estimates using standard pregnancy dating. It does not diagnose, predict your delivery date, or replace prenatal care. Your OB or midwife determines your actual due date and delivery plan.
Keep track of both babies, week by week
The Twin Pregnancy App follows both twins through every week — per-baby sizes, a due-date countdown, appointment tracking, and double planning. Private by design, offline, and free.
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