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Asked: 2026-06-15T13:53:08+00:00

Possible Duplicate: Is JavaScript’s Floating-Point Math Broken? Note – I have read other posts

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Possible Duplicate:
Is JavaScript’s Floating-Point Math Broken?

Note – I have read other posts on parseFloat(), but I have not found a good explanation as to why the problem occurs. (Or I just didn’t understand it).

This code …

var sum = parseFloat("1.001") + parseFloat(".001");

alert(parseFloat(sum));​

outputs …

1.0019999999999998

I’ve read that adding sum.toFixed(2) will include only 2 decimal points.

However, I do not 100% understand why this long decimal occurs.

Does parseFloat(sum) represent sum in binary? If so, then 1.001 cannot be represented in binary since 1/2^x + … can never equal .001 or 1/1000 exactly?

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1 Answer

  1. Editorial Team

    This isn’t specific to Javascript, but rather how IEEE Floating Point Numbers are represented internally that cause precision errors.

    I won’t reproduce the content here, but there are a bunch of resources available to help explain what is going on in your example.

    Here is one: http://www.petebecker.com/js/js200006.html

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