Multiplication int and float(double) in JavaScript

Question

I want to make multiplication using JavaScript.

Multiplication of 2 and 0.15 is 0.3 but 3 and 0.15 is 0.44999999999999996. I want to get 0.45 such as result. How can I do it with JavaScript?

There is no `int` or `float` in JavaScript. Everything is a `double`. That being said, you're looking for [`toFixed()`](https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Number/toFixed) if you want to convert your value into a string. — Zeta, May 17 '13 at 11:44
See this: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Math/round — Henrik Andersson, May 17 '13 at 11:44
Yup, it is always the JavaScript, which is broken! Floating point are the same in all languages, and they obey the rules in IEEE 754. — Bakudan, May 17 '13 at 11:48
same if you add `0.15+0.15+0.15 = 0.44999999999999996`, but weird that `3.15*3=9.45` lol — Jaider, Sep 29 '22 at 01:45
you can multiply by 100 then divided by 100... so `0.15 x 100 = 15`... `15 * 3 = 45`... `45/100 = 0.45` ... but can risk overflow for large numbers — Jaider, Sep 29 '22 at 14:08

score 22 · Accepted Answer · answered May 17 '13 at 11:45

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It's a rounding error. You may want to round your number to a fixed amount of digits, like this:

parseFloat((your_number).toFixed(2));

answered May 17 '13 at 11:45

Simon M

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It's nice, but it produces a String FWIW! – Henrik Andersson May 17 '13 at 11:45
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@mplungjan Yeah, I know that, OP might not. – Henrik Andersson May 17 '13 at 11:46
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@limelights You have a good point, I forgot about the return type... I'll update the answer with `parseFloat` – Simon M May 17 '13 at 11:47
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http://jsfiddle.net/mplungjan/z4GkK/ – mplungjan May 17 '13 at 11:49
`12.5 * 1.15` = `14.374999999999998` ---> `parseFloat(12.5 * 1.15).toFixed(2);` is `14.37` which is wrong. You need to do this: `parseFloat(parseFloat((12.5 * 1.15).toFixed(3)).toFixed(2));` – Kevin O. Jan 03 '23 at 12:19
Plain vanilla solution: `new Intl.NumberFormat('en-US').format(12.5 * 1.15);` – Kevin O. Jan 03 '23 at 12:55
Also, you can use: `(Math.round((12.5 + Number.EPSILON) * 100) * 1.15 / 100).toFixed(2)` – Kevin O. Jan 03 '23 at 13:25

score 9 · Answer 2 · answered May 17 '13 at 11:46

Unfortunately this happens in any language using floating point arithmetic. It's an artifact arising when floating point operations are encoded into binary, operations performed, and decoded from binary to report the answer in a form you'd expect.

Depending on what you want to do with the output, you can call a round()-like function to round to a number of decimal places or compare the output to a value using a (small) number called a tolerance. E.g. two numbers are considered equal if their absolute difference is less than this tolerance.

Multiplication int and float(double) in JavaScript

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