Everyday due date problems come down to one relationship between my average cycle lasts, i conceived on, my last period started on, method, today’s date and one way. This calculator turns those numbers into days of pregnancy completed, pregnancy completed in and you are in week, with the working shown so you can check the result rather than simply trust it.
What Is the Due Date Calculator?
The due date calculator gives you an estimate of days of pregnancy completed, pregnancy completed in and you are in week based on my average cycle lasts, i conceived on, my last period started on, method, today's date and one way.
It is a quick reference figure rather than a diagnosis, and it is most useful for tracking how a number moves over time rather than for interpreting a single reading.
How the Due Date Estimate Is Worked Out
The calculation follows published reference relationships, so it is a reasonable approximation when the inputs are accurate. It assumes an average adult and does not account for individual variation.
If you are comparing two people, or the same person over a period of weeks, keep the method and the inputs identical. A change in the method can easily look like a change in the person.
What This Calculator Does Not Do
It does not diagnose anything, and it does not replace advice from a clinician. If a figure comes out at an extreme, or if it differs sharply from what you expect, that is a reason to speak to a professional rather than to adjust the inputs.
Nothing you type here is stored or sent anywhere. The whole calculation happens in your browser.
A Worked Example
Working through an example, with my average cycle lasts set to 21, i conceived on set to 10, my last period started on set to 5, the calculator returns birth due date of 527,993, and birth due date (birth due date cd) of 10,280, and beginning of 527,979. Substitute your own figures and the same steps produce the same kind of answer.
Frequently Asked Questions
What do I need to work out days of pregnancy completed?
Enter my average cycle lasts, i conceived on, my last period started on, method, today's date and one way. The calculator then works through the relationship and reports days of pregnancy completed, pregnancy completed in and you are in week.
What does the due date actually calculate?
It takes my average cycle lasts, i conceived on, my last period started on, method, today's date and one way and converts them into days of pregnancy completed, pregnancy completed in and you are in week using the standard relationship for this problem. Each step is applied in turn, so every output is traceable back to the numbers you typed in.
How should I enter my average cycle lasts?
Use the value you actually have, in the unit shown next to the field. Enter every value in the same unit system. The calculator assumes the figures you supply are consistent, so it cannot correct a mistake that happens before the calculation starts.
Can I use this for a quick estimate as well as a precise answer?
Yes. The calculator is built for quick checks, so round your inputs to a sensible number of significant figures and the result will be just as useful. If you need more precision, keep the same method and add digits to the inputs rather than adjusting the method itself.
Why does a small change in one value move the answer so much?
That happens when an output depends on a ratio, because dividing by a small number magnifies any change in it. Check the units first, then check whether the value you entered is in the range the relationship was designed for.