Due Date Calculator
Estimate your due date from your last period or conception date, see how many weeks along you are today, and map out the trimester milestones ahead.
Counting down to your baby
A due date turns an abstract nine months into a real date on the calendar — a peg to plan appointments, leave, and the nursery around. Because it's built from your cycle, it's only ever an estimate, but it's the number every scan, checkup, and growth chart is measured against.
Once your baby arrives, plan the days ahead with the Baby Feeding Amount Calculator and the Baby Sleep Schedule Planner, or budget the year with the First-Year Baby Cost Estimator.
Frequently Asked Questions
How is the due date calculated?
From your last menstrual period (LMP), the estimate uses Naegele's rule: 280 days (40 weeks) after the first day of your last period for a 28-day cycle, adjusted up or down if your cycle runs longer or shorter. From a known conception or ovulation date, it counts forward 266 days (38 weeks). Both methods land on the same date when conception is 14 days after the LMP, which is the textbook assumption.
Why does my cycle length matter?
The 40-week figure assumes ovulation on about day 14 of a 28-day cycle. If your cycles are longer, you ovulate later, so conception and the due date shift later too — and the reverse for shorter cycles. Entering your average cycle length nudges the LMP estimate to fit your body rather than the textbook average.
How accurate is a due date?
It's an estimate, not an appointment. Only about 1 in 20 babies are born on their exact due date; most arrive in the two weeks either side, and a full-term birth is anything from 37 to 42 weeks. An early ultrasound (dating scan) is the most accurate way to date a pregnancy, especially if your cycles are irregular or you're unsure of your LMP.
Is this a substitute for prenatal care?
No. This tool is for information and planning only — it can't assess your pregnancy, and it doesn't replace your OB, midwife, or a dating ultrasound. Use it to orient yourself, then confirm your dates and any concerns with your healthcare provider.
Informational estimate only, not medical advice. Only a dating ultrasound and your OB or midwife can confirm your due date — consult your healthcare provider about your pregnancy.