Generate Random Numbers Within a Range using JavaScript

August 5, 2010

Generate Random Numbers Within a Range using JavaScript

Thursday, August 05, 2010 Posted by Suprotim Agarwal
Labels: JavaScript

A formula for generating a random number within a given range using JavaScript is as follows:

Math.floor(Math.random() * (UpperRange - LowerRange + 1)) + LowerRange;

So to generate a random number between 25 and 75, the equation would be

Math.floor(Math.random() * (75-25+1)) + 25;

i.e.

Math.floor(Math.random() * 51) + 25;

Here’s the entire code:

<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>Random Number in JavaScript</title>
    <script type="text/javascript">
        var randomNumber = Math.floor(Math.random() * 51) + 25;
        document.write("<p>" + randomNumber + "</p>");      
    </script>
</head>
<body>
</body>
</html>

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About The Author

Suprotim Agarwal, ASP.NET Architecture MVP works as an Architect Consultant and provides consultancy on how to design and develop Web applications.

Suprotim is also the founder and primary contributor to DevCurry, DotNetCurry and SQLServerCurry. He has also written an EBook 51 Recipes using jQuery with ASP.NET Controls.

Follow him on twitter @suprotimagarwal

comments

2 Responses to "Generate Random Numbers Within a Range using JavaScript"

Ben Archer said...

March 2, 2011 6:12 PM

Thanks! What if I want it to be equal than or greater to X, but less than Y?

benjamin.morse.archer@gmail.com
Suprotim Agarwal said...

March 2, 2011 9:18 PM

Ben: In that case use the following:

Math.floor(Math.random()*(Y-X)) + X;

Although I have not tested it, but it should work!