Pregnancy Due Date Calculator
Three methods to compute an Estimated Date of Delivery (EDD): **LMP** uses Naegele's rule (LMP + 280 days) with optional cycle-length adjustment. **Conception** counts 266 days from conception. **Ultrasound** back-calculates LMP from the scan date and reported gestational age, then projects forward 280 days. Shows current weeks/days along, trimester (1: 0–12w, 2: 13–26w, 3: 27w+), and days remaining or overdue.
Estimated due date
Friday, May 28, 2027
280 days to go
Currently
0w 0d
Trimester 1
Approx. conception: Friday, September 4, 2026
About: Estimates only. ~4% of babies arrive on their EDD; ~80% within 2 weeks. Defer to your clinician's dating.
How to use
- Pick a method: LMP (most common), conception (if known), or ultrasound dating (most accurate first trimester).
- Enter the dates. For LMP, optionally adjust cycle length away from 28 days.
- See your due date, current week, and trimester.
Frequently asked questions
- How accurate is this?
- An estimate, not a prediction. Only ~4% of babies are born on their EDD; ~80% within 2 weeks of it. Ultrasound dating in the first trimester is the most accurate method.
- LMP says EDD but conception date says something different?
- Cycle length matters. Naegele's rule assumes a 28-day cycle (conception ~day 14). If yours is longer/shorter, adjust the cycle length input — or use the conception or ultrasound method.
- Why 280 days, not 9 months?
- Naegele's 1812 rule was set at 280 days (40 weeks) from LMP because that matched observed averages. Most calendars treat 'months' as ~30.4 days, so 9 months and 280 days are close but not identical.
- Is this medical advice?
- No. It's a math tool. Always defer to your OB/GYN's dating, especially after a first-trimester ultrasound — their EDD takes precedence over any calculator's.
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