How accurate is the due date calculator?

This calculator gives an estimate based on your menstrual dates. An early ultrasound (before 13 weeks) is the most accurate way to confirm your due date, especially if your cycles are irregular.

What does 40 weeks mean?

Pregnancy is counted from the first day of your last period, not from conception. So weeks 1–2 are actually before conception. Weeks 3–40 cover the actual development period. A full-term pregnancy is 37–42 weeks.

What if my cycle length isn't 28 days?

Our calculator adjusts for cycle length. If your cycle is longer than 28 days, ovulation (and likely conception) occurred later, so the due date is pushed forward. Shorter cycles shift it back.

Can I use the conception date instead?

If you know your conception date, add 266 days (38 weeks) to get your estimated due date. Our calculator uses LMP because conception dates are often uncertain.

Pregnancy Due Date Calculator — Free EDD Estimator

The Pregnancy Due Date Calculator estimates your baby's estimated due date (EDD) using Naegele's Rule — the standard obstetric method used worldwide. Your due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period. Only about 5% of babies are born exactly on their due date, but knowing your EDD helps you plan, track milestones, and prepare for arrival. Enter your last period date below for an instant estimate.

Days since last menstrual period(days ago)

Average cycle length(days)

Frequently Asked Questions

The standard method (Naegele's Rule) adds 280 days (40 weeks) to the first day of your last menstrual period. This assumes a 28-day cycle. Our calculator adjusts for longer or shorter cycles.

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