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    <blockquote> <p>we get exactly 0.012</p> </blockquote> <p>No you don't. Neither <code>float</code> nor <code>double</code> can represent 3/250 exactly. What you do get is a value that is rendered by the string formatter <code>Double.ToString()</code> as <code>"0.012"</code>. But this happens because the formatter doesn't display the exact value.</p> <p>Going through <code>decimal</code> is causing rounding. It is likely much faster (not to mention easier to understand) to just use <code>Math.Round</code> with the rounding parameters you want. If what you care about is the number of significant digits, see:</p> <ul> <li><a href="https://stackoverflow.com/questions/374316/round-a-double-to-x-significant-figures">Round a double to x significant figures</a></li> </ul> <hr> <p>For what it's worth, <code>0.012f</code> (which means the 32-bit IEEE-754 value nearest to 0.012) is exactly</p> <pre><code>0x3C449BA6 </code></pre> <p>or</p> <pre><code>0.012000000104308128 </code></pre> <p>and this is <em>exactly</em> representable as a <code>System.Decimal</code>. But <code>Convert.ToDecimal(0.012f)</code> won't give you that exact value -- per <a href="http://msdn.microsoft.com/en-us/library/he38a8ca.aspx" rel="nofollow noreferrer">the documentation there is a rounding step</a>.</p> <blockquote> <p>The <code>Decimal</code> value returned by this method contains a maximum of seven significant digits. If the value parameter contains more than seven significant digits, it is rounded using rounding to nearest. </p> </blockquote>
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    1. POWhen is it beneficial to convert from float to double via decimal
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    1. COBut why would rounding to a more "coarse" value occur when `decimal` has much better precision?
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    2. CO@Jon: The set of values representable by `decimal` are not a superset of those representable by `double`. Take `eps = double.Epsilon` and compare `(decimal)eps`, `(decimal)(2 * eps)` and `(decimal)(3 * eps)` and then tell me that `decimal` has much better precision.
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    3. CO@Jon: Here, I did it for you: http://ideone.com/TQJklg Obviously rounding can occur when converting a float to `decimal`.
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