Estimate your due date and key milestones based on the first day of your last menstrual period.
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One of the first questions after a positive test is "when am I due?" This calculator uses the same clinical method your doctor will likely use at your first visit — instantly, and free.
We use Naegele's Rule: adding 280 days (40 weeks) to the first day of your last menstrual period, adjusted for cycle length if it's longer or shorter than the standard 28 days.
Only about 5% of babies are born exactly on their due date. Your doctor's ultrasound dating, especially in the first trimester, is more precise than a calendar-based estimate like this one.
If you're trying to pin down your cycle, our Ovulation Calculator can help, and our Calorie & TDEE Calculator in Nutrition is a useful starting point for pregnancy nutrition planning alongside your doctor's guidance.
It's a solid starting estimate using the standard clinical formula, but an early ultrasound from your doctor is considered more accurate, especially if your cycle is irregular.
Use your best estimate — if you have an ultrasound date from your doctor, that will be more reliable than a calculated estimate.
Enter your actual average cycle length — the calculator adjusts the estimate accordingly, since longer or shorter cycles shift the likely conception and due dates.