Searching “due date calculator” usually lands you on a page buried under ads, a signup wall, or a pregnancy app you have to install just to see one number. The math behind it is simple and has been for over a century: count forward from your last period, or from conception if you know it. We built a free calculator that does that math right here, updates the moment you change a date, and never asks for an account.
Estimate your due date now
Pick a calculation method, set a date, and the due date, current week, and timeline below update immediately.
How to use it
Start by choosing a method: the first day of your last menstrual period, or a known date of conception. Set the date with the picker, or nudge it a day at a time with the plus and minus buttons next to it. There is no calculate button. Every change instantly updates the headline, the current gestational week and day, which trimester you are in, and the 40-week bar that fills in as the pregnancy progresses.
The last period method applies Naegele’s rule, adding 280 days to that date. The conception method adds 266 days instead, since conception typically happens about two weeks after a period starts. Switch between the two at any time and the underlying due date stays consistent. A small size comparison below the timeline turns the current week into a plain-language size, purely for a sense of scale rather than any clinical measurement. Your last method and date are saved on your device, so returning to the page shows your own numbers, not a stranger’s default.
How it compares to a pregnancy tracking app
A dedicated pregnancy app and this calculator solve overlapping but different problems. The app is built for months of ongoing use: symptom logs, weight and appointment tracking, week-by-week articles, kick counters, and reminders that follow you the whole way to delivery. Getting that experience usually means creating an account and keeping the app installed on your phone for the better part of a year.
Our calculator answers the one question that sends most people searching in the first place: given a date, what is the estimated due date, and how far along does that make me right now? It runs the same standard math a tracking app runs for this specific calculation, draws it on a timeline, and stops there. We left out symptom logging, reminders, and any kind of long-term account, on purpose. A page you land on from a search result should answer that one question in a few seconds, not ask you to sign up first.
This is a standalone free tool, not a companion app to any specific pregnancy tracker. If you want ongoing tracking through the following months, a dedicated pregnancy app is the better fit. If you just want today’s estimate without installing anything, this covers it.
FAQ
How is a pregnancy due date calculated?
The most common method, called Naegele’s rule, adds 280 days (40 weeks) to the first day of your last menstrual period. If you know your conception date instead, add 266 days (38 weeks) to that, since conception usually happens around two weeks into a cycle. Both methods land on roughly the same estimate.
Can I calculate my due date online without an app?
Yes. This calculator runs entirely in the browser tab you are reading right now, so there is nothing to install. Pick last period or conception date, enter a date, and the due date, current week, and trimester update immediately.
How accurate is a due date calculator?
It is an estimate, not a diagnosis. Only a small share of babies arrive on the exact calculated date; most arrive within a couple of weeks either side of it. Cycle length, irregular ovulation, and individual variation all shift the real date earlier or later than a simple calculation predicts. An ultrasound dating scan generally narrows the estimate further than date math alone can.
Is my data private?
Yes, by design. The calculator stores your inputs only in your browser’s local storage, on your own device. There is no server, no account, and no analytics, and the tool makes zero network requests once the page has loaded. The “Clear my data” button removes everything it saved.
Does it work offline?
Once the page has loaded, yes. The calculator is a single self-contained file with no external requests, so it keeps working without a connection, and your saved inputs are still there when you come back.
Is this medical advice?
No. This tool estimates timelines from standard date math and is meant for general planning, not diagnosis or care decisions. Talk to a doctor or midwife to confirm dates and monitor a pregnancy properly.
