Pregnancy Due Date Calculator — Naegele's Rule
By ToolZoneX Team
•
August 2026
This calculator estimates your due date using Naegele's Rule, the standard formula clinicians use: due date = first day of your last menstrual period (LMP) + 280 days (40 weeks), assuming a regular 28-day cycle.
How to Use Pregnancy Due Date Calculator
1.
Enter the first day of your last menstrual period2.
View your estimated due date, current gestational week, and trimester instantly
Key Features
- Uses the standard Naegele's Rule formula
- Shows current gestational week and day
- Identifies which trimester you are in
When to Use This Tool
•
Getting a quick due date estimate before a prenatal visit•
Tracking which week and trimester of pregnancy you are in•
Planning for milestones like the anatomy scan or maternity leave
Frequently Asked Questions
Only about 5% of babies arrive exactly on their due date — most arrive within a couple weeks before or after. It assumes a regular 28-day cycle, so it is less accurate for irregular cycles. This is an estimate only, not a substitute for medical advice.
Conception date is rarely known precisely, but the start of the last period is easier to remember and correlates predictably with typical ovulation timing.
Ready to get started?
Open Pregnancy Due Date CalculatorRelated Tools
Pregnancy Due Date Calculator
Use Pregnancy Due Date Calculator now