Calculate a Pregnancy Due Date, Free
A pregnancy due date calculator gives a quick estimate of when a baby is likely to arrive, using the same standard method most care providers start with. Here is how the calculation actually works, and how to run it free online in a few seconds.
How a due date calculator estimates the date
The standard method adds 280 days, 40 weeks, to the first day of the last menstrual period. This is the same baseline "naegele's rule" style estimate most care providers use as a starting point, though it assumes a fairly typical cycle length. If the conception date is known instead, the calculator can estimate from that date directly rather than the last period.
How to calculate a due date online for free
- Open the Pregnancy Due Date Calculator.
- Enter the first day of your last menstrual period, or a known conception date.
- The estimated due date appears instantly.
Why the estimate can shift
This calculation is a general estimate, not a diagnosis. A care provider may adjust the date based on an ultrasound, especially if the cycle length was not exactly typical, since ultrasound measurements of the fetus can be more precise than a date-based calculation alone. Only about 1 in 20 babies actually arrive on the exact estimated date, the estimate is a planning window, not a guarantee.
Is this free, and is anything saved?
Yes, the calculator is completely free to use with no sign-up. The calculation runs entirely in your browser, so the dates you enter are never saved or sent anywhere.
Questions
Frequently asked
Is this due date calculator free?
Yes, completely free to use, with no sign-up, and your dates are never saved or sent anywhere.
Is this the same method doctors use?
It uses the standard 280-day (40-week) estimate from the last menstrual period, the same baseline method commonly used, though a care provider may adjust the date based on an ultrasound.
Can I calculate from a known conception date instead of the last period?
Yes, the tool supports estimating from either the last menstrual period date or a known conception date.
Is this medical advice?
No. This is a general estimate for planning purposes, not medical advice. Follow your care provider’s guidance for your actual due date and prenatal care.