Pregnancy Due Date Calculator
Estimate due date and current week using Naegele's rule.
About this tool
This uses Naegele's rule — the standard estimate of adding 280 days (40 weeks) to the first day of your last menstrual period — to project a due date, and shows how many weeks along you are today.
Key Features
- Estimated due date
- Current gestational week
- Local-date accurate (no timezone drift)
How to Use
- Enter the first day of your last menstrual period.
- Click Calculate Due Date.
Benefits
- Quick estimate to plan around
- See your current week at a glance
- Cross-check against your provider's estimate
Frequently Asked Questions
It's a standard estimate assuming a 28-day cycle with ovulation on day 14 — only about 5% of babies actually arrive on the exact calculated date. Your healthcare provider may adjust the date using an ultrasound, which is more accurate for irregular cycles.
Naegele's rule assumes a 28-day cycle. If yours is longer or shorter, the real due date shifts accordingly — your provider can adjust for this, especially with early ultrasound dating.