Due Date Calculator
How many weeks along today, and how long is left.
Reading your result
Fill in every field and the steps will be spelled out here.
How it is calculated
Gestational age counts from the last period, not from conception. Four weeks pregnant means roughly two weeks since conception — the earlier date is used because it is the one that can actually be observed.
Around one birth in twenty arrives on the estimated date. Thirty-seven to forty-two weeks is term, and first babies tend to run late. The date is a midpoint, not a deadline.
Irregular cycles undermine the calculation. The rule assumes a 28-day cycle, and while this calculator adjusts for a different length, it cannot adjust for ovulation that moves from month to month. A dating scan is substantially more accurate.
Frequently asked questions
My scan gives a different date.
Follow the scan. Early scans measure the fetus directly and are not affected by cycle irregularity, so a clinically revised date supersedes this one.
How are trimesters divided?
First through week 13, second through week 27, third to birth. The split matters because screening and precautions differ across them.
Does it apply to twins?
The date is calculated the same way, but multiples commonly arrive before 37 weeks and are managed on a different schedule.
An estimate from Naegele's rule that commonly differs from the actual date. Clinical assessment, including ultrasound dating, takes precedence.