Pregnancy Due Date Calculator 📅
Find your estimated due date using your last period, conception date, IVF transfer, or ultrasound measurements.
How the Due Date Calculator Works
Our pregnancy due date calculator uses four medically recognized methods to estimate when your baby will arrive. Each method applies standard obstetric formulas used by healthcare professionals worldwide, giving you the most accurate estimate possible based on the information you provide.
Last Menstrual Period (LMP) Method — Naegele's Rule
The most commonly used method, Naegele's Rule, calculates your due date by adding 280 days (40 weeks) to the first day of your last menstrual period. This assumes a 28-day cycle with ovulation occurring on day 14. If your cycle is shorter or longer than 28 days, the calculator adjusts by adding or subtracting the difference.
Conception Date Method
If you know the date of conception, the calculator adds 266 days (38 weeks). This is 14 days less than the LMP method because it starts from the actual moment of fertilization rather than the beginning of the menstrual cycle.
IVF Transfer Date Method
For IVF pregnancies, the due date is calculated from the embryo transfer date. A Day 3 embryo transfer adds 263 days, while a Day 5 (blastocyst) transfer adds 261 days. These calculations are the most precise of all methods because the exact age of the embryo is known.
Ultrasound-Based Method
When you have an ultrasound, the technician measures the baby to determine gestational age. Our calculator takes the ultrasound date and the gestational age measured, then projects forward to the 40-week mark. First-trimester ultrasounds are considered the gold standard for dating.
Remember that an estimated due date is just that — an estimate. Only about 5% of babies arrive on their exact due date, but approximately 80% arrive within two weeks of it.