Due Date Calculator

This calculator uses Naegele's Rule, the standard method used by most OB-GYNs. Only about 5% of babies arrive on their exact due date — but 90% arrive within 2 weeks of it.

Use your last menstrual period (LMP) if you know it — it's the most accurate for regular 28-day cycles. Use conception date if you tracked ovulation precisely or conceived via IVF.

Add 280 days (40 weeks) to the first day of your last period, or 266 days (38 weeks) to your conception date. If your cycle isn't 28 days, the tool adjusts automatically.

Week 1 starts on the first day of your last menstrual period — before conception even happens. By the time you get a positive test, you're typically 4–5 weeks pregnant.

Yes — use the 'Average cycle length' field. If your cycle is 32 days instead of 28, the tool adds the extra 4 days to your due date calculation.