Enter the first day of your last menstrual period and your average cycle length to get your estimated due date (EDD), current gestational age, and conception date. The Baby Due Date Calculator uses Naegele's Rule — adding 280 days to your LMP — to give you a reliable pregnancy timeline at a glance.
Estimated Due Date
--
Estimated Conception Date
--
Current Gestational Age
--
Current Trimester
--
Days Until Due Date
--
Your estimated due date (EDD) is calculated using Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP), then adjust based on your cycle length. If your cycle is longer or shorter than 28 days, the calculator shifts the date accordingly. This method is used by most doctors and midwives as a standard starting point.
An EDD based on LMP is a reliable estimate, but only about 5% of babies are born exactly on their due date. Most births happen within two weeks before or after the due date. An early ultrasound (especially between 8–12 weeks) is the most accurate way to confirm your due date and may override the LMP-based calculation.
Yes, your due date can change. If an ultrasound shows that your baby's size doesn't match the LMP-based date by more than a certain number of days, your healthcare provider may update your EDD. Changes are most common when the LMP date is uncertain or if you have irregular cycles.
If you already have a due date from your doctor or ultrasound, you can work backwards to estimate your LMP by subtracting 280 days. This calculator is best used for estimates — always rely on the due date confirmed by your healthcare provider for clinical decisions.
Statistically, only about 5% of women give birth on their exact due date. Around 80% of births occur within two weeks of the EDD. The due date is best treated as the midpoint of a normal delivery window rather than a precise target.
Most home pregnancy tests can detect the hCG hormone as early as the first day of a missed period, which is roughly 14 days after conception. Some sensitive tests claim to detect pregnancy 5–6 days before a missed period, but accuracy increases closer to your expected period date.
Pregnancy is divided into three trimesters: the first trimester covers weeks 1–12, the second trimester covers weeks 13–26, and the third trimester spans weeks 27–40 (and beyond, if necessary). Each trimester marks different stages of fetal development and maternal changes.
Gestational age is the age of the pregnancy measured in weeks from the first day of your last menstrual period — not from conception. A full-term pregnancy is typically 40 weeks of gestational age. Your doctor may also use ultrasound measurements to estimate or confirm gestational age.