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    <p>Dogbert's answer is good, but if your code might have to deal with negative numbers, <code>Math.floor</code> by itself may give unexpected results.</p> <p>E.g. <code>Math.floor(4.3) = 4</code>, but <code>Math.floor(-4.3) = -5</code></p> <p>Use a helper function like this one instead to get consistent results:</p> <pre><code>truncateDecimals = function (number) { return Math[number &lt; 0 ? 'ceil' : 'floor'](number); }; // Applied to Dogbert's answer: var a = 5.467; var truncated = truncateDecimals(a * 100) / 100; // = 5.46 </code></pre> <p>Here's a more convenient version of this function:</p> <pre><code>truncateDecimals = function (number, digits) { var multiplier = Math.pow(10, digits), adjustedNum = number * multiplier, truncatedNum = Math[adjustedNum &lt; 0 ? 'ceil' : 'floor'](adjustedNum); return truncatedNum / multiplier; }; // Usage: var a = 5.467; var truncated = truncateDecimals(a, 2); // = 5.46 // Negative digits: var b = 4235.24; var truncated = truncateDecimals(b, -2); // = 4200 </code></pre> <p>If that isn't desired behaviour, insert a call to <code>Math.abs</code> on the first line:</p> <pre><code>var multiplier = Math.pow(10, Math.abs(digits)), </code></pre> <p><strong>EDIT:</strong> shendz correctly points out that using this solution with <code>a = 17.56</code> will incorrectly produce <code>17.55</code>. For more about why this happens, read <a href="http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html" rel="noreferrer">What Every Computer Scientist Should Know About Floating-Point Arithmetic</a>. Unfortunately, writing a solution that eliminates all sources of floating-point error is pretty tricky with javascript. In another language you'd use integers or maybe a Decimal type, but with javascript...</p> <p>This solution <em>should be</em> 100% accurate, but it will also be slower:</p> <pre><code>function truncateDecimals (num, digits) { var numS = num.toString(), decPos = numS.indexOf('.'), substrLength = decPos == -1 ? numS.length : 1 + decPos + digits, trimmedResult = numS.substr(0, substrLength), finalResult = isNaN(trimmedResult) ? 0 : trimmedResult; return parseFloat(finalResult); } </code></pre> <p>For those who need speed but also want to avoid floating-point errors, try something like <a href="https://github.com/dtrebbien/BigDecimal.js" rel="noreferrer">BigDecimal.js</a>. You can find other javascript BigDecimal libraries in this SO question: <a href="https://stackoverflow.com/q/744099/224354">"Is there a good Javascript BigDecimal library?"</a> and here's a good blog post about <a href="http://blog.smartbear.com/testing/four-serious-math-libraries-for-javascript/" rel="noreferrer">math libraries for Javascript</a> </p>
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    1. POTruncate (not round off) decimal numbers in javascript
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    1. USNick Knowlson
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    1. COWhy unexpected? Changing the direction of rounding when you go below 0, causes all sorts of arithmetical artefacts & crappy math. For example, twice as many numbers will round to 0, as any other integer. For graphics, accounting & many other uses, you'll get crappy results. To tell you the truth, it'd be harder to say what your suggestion is *good* for as to say what it's *not*.
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      1. USThomas W
    2. COIt's good for exactly what it says - when you want to truncate decimals rather than rounding.
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    3. CONot going to work with 17.56 because browser gives 17.56 * 100 = 1755.9999999999998 not 1756
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