Twins Due Date Calculator
Calculate estimated due date for a twin pregnancy. Twin pregnancies typically deliver 3–5 weeks earlier than singletons.
Part of our Health Calculators collection.
Twins Due Date Calculator
Free online calculator
Results update automatically as you type
How to Use This Calculator
- 1
Enter first day of last period.
- 2
See estimated due dates for identical and fraternal twins.
Twin Pregnancy Timeline
Singleton full term: 40 weeks (280 days from LMP) Identical twins avg: 36.9 weeks (259 days from LMP) Fraternal twins avg: 37.6 weeks (263 days from LMP) Twin pregnancies have higher risk of preterm birth. Most twin deliveries: 36–38 weeks.
Example Calculation
Example: LMP January 1, 2025
Inputs
lmpDate: 2025-01-01
Result
Identical twins: ~Sep 17 | Fraternal: ~Sep 21
Jan 1 + 259 days = Sep 17. Vs singleton Oct 8.
Frequently Asked Questions
Why do twins deliver earlier?
The uterus runs out of space, placental function may be reduced with two babies, and the risk of preterm labor increases. Doctors typically plan delivery by 38 weeks even for uncomplicated twin pregnancies.
Are twins at higher risk?
Yes — twin pregnancies have higher rates of preterm birth, low birth weight, gestational diabetes, preeclampsia, and cesarean delivery. More frequent prenatal monitoring is standard.