Pregnancy Due Date Calculator
Estimate your baby's arrival and trimester.
Uses Naegele's rule (last period + 280 days). This is an estimate — only an ultrasound and your doctor can confirm a due date.
About the Due Date Calculator
Free pregnancy due date calculator. Enter the first day of your last period to estimate your due date, current week of pregnancy and trimester.
Everything is calculated instantly in your browser — nothing you type is uploaded or stored. Bookmark Calcooly for the next time you need it.
How to use the Due Date Calculator
- 1Enter the first day of your last period.
- 2See your estimated due date instantly.
- 3Check how far along you are and your current trimester.
Frequently asked questions
How is the due date estimated?+
It uses Naegele's rule — 280 days (40 weeks) from the first day of your last period.
How accurate is it?+
It's an estimate. Only an ultrasound and your doctor can confirm a due date, and cycle length can shift the result.
Is the result exact?+
It's a reliable estimate for general information. For important financial, medical or legal decisions, check with a qualified professional.