Free EDD Calculator

An EDD calculator (Estimated Due Date calculator) is a tool that calculates your expected delivery date. It uses Naegele's Rule — adding 280 days (40 weeks) to the first day of your last menstrual period — or calculates from conception date, IVF transfer date, or ultrasound gestational age. Our free estimated due date calculator supports all four methods and automatically adjusts for your cycle length.

Our EDD calculator provides a close estimate based on proven medical formulas. However, only about 5% of babies are born on their exact estimated due date. A normal full-term birth can happen anywhere from 37–42 weeks. The most accurate method is an early first-trimester ultrasound (before 14 weeks), which your OB-GYN or midwife will use to confirm your estimated due date.

Our LMP calculator automatically adjusts for your cycle length. If your cycle is longer (e.g., 35 days), ovulation occurs later, so the due date is adjusted forward. If it's shorter (e.g., 24 days), it's adjusted back. Simply use the cycle length slider when selecting the LMP method.

Your healthcare provider will typically confirm or adjust your due date at your first prenatal visit, usually around 8–10 weeks. If the ultrasound measurement differs from the LMP-based calculation by more than 5–7 days, the ultrasound date is usually used instead.

Gestational age (GA) is counted from the first day of your last menstrual period — this is the medical standard used worldwide. Fetal age (also called developmental age) counts from conception, which is typically about 2 weeks later. All dates shown in this calculator use gestational age.

For IVF Day 3 transfers, we add 263 days to the transfer date (280 days minus 17 days for the 3-day embryo age). For Day 5 blastocyst transfers, we add 261 days (280 minus 19). This accounts for the embryo's age at transfer.

The EDD calculation is the same regardless of the number of babies. However, twin and higher-order pregnancies are typically delivered earlier than singleton pregnancies — often around 36–37 weeks for twins. Your doctor will discuss timing based on your specific situation.

A pregnancy lasting beyond 40 weeks is common. Most providers will schedule additional monitoring after 41 weeks and discuss induction options. Only about 5% of births occur on the estimated due date; most happen within 2 weeks before or after.