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![Mike Staebell](https://uploads.teamtreehouse.com/production/profile-photos/457992/micro_mike_copy.jpg)
Mike Staebell
6,177 PointsPercentage values
What's the significance of the percentages Guil is using? (For example, he's using something like width:65.123456789%.) Why not just round up or down? I don't understand the need to use 8+ decimal points. I'm probably missing something.
4 Answers
![James Barnett](https://secure.gravatar.com/avatar/43ea08b4fc547e8a5da87c207bea2123?s=96&d=https%3A%2F%2Fecs-static.teamtreehouse.com%2Fassets%2Fcontent%2Fdefault_avatar-445fbbabfc8dc9188fb5967fe43322ee0c3e0dd1e10f378bf8343784af5a13eb.webp&r=pg)
James Barnett
39,199 PointsRounding errors mainly due to the way the math works out. In my own work, I round up to 3 decimal places.
further reading: http://nimbupani.com/using-decimal-percentage-values-in-responsive-design.html
![Evandro Camargo](https://uploads.teamtreehouse.com/production/profile-photos/551772/micro_avatar2_512.jpg)
Evandro Camargo
14,187 PointsIt's probably just to the fact that, the more precise you get, the less gaps and "white spaces" you would find. As you can never go 102% of total width without having a horizontal scroll bar or just that 99.89% isn't the same as 100% when it comes to precision. On smaller screens that point-something % could be insignificant but at some point it might render something worth 10 or even 20 pixels of unused or unspecified space with some high-density or wide resolution viewports.
As long as that doesn't matter to you, it should be ok to round up or down. :) Again, as I said back in another post, this is just my 2 cents and opinion. I might have been misled at something believing such would be the case (as I've asked myself the same question when I first saw that, but then came to that conclusion.).
![Mike Staebell](https://uploads.teamtreehouse.com/production/profile-photos/457992/micro_mike_copy.jpg)
Mike Staebell
6,177 PointsThanks, Evandro. I follow your logic. Those extra pixels definitely matter to me. But I can't help but wonder what originally caused the need for that many decimal points? If you use whole numbers for all of your padding/margins, wouldn't that allow you to stick with whole numbers?
For example, if you set a margin of 5% and a padding of 10%, the width of the viewport would be 70% (since 5x2 + 10x2 = 30% worth of padding/margins)
Is it because he used pixels in some cases? I'm no math whiz, but I could see how that might break the percentage values into numerous decimal points.
![Evandro Camargo](https://uploads.teamtreehouse.com/production/profile-photos/551772/micro_avatar2_512.jpg)
Evandro Camargo
14,187 PointsWell, there we go. That was, in fact, the reason. But as we learn there, there might be no real point to use precision above 3 decimals or maybe we could consider using the calc() CSS function and provide the 3 decimals fallback option for older browsers.
I think that Guil just tried to illustrate that decimal precision on percentages DO matter. From there we learn it and adapt it to real world needs. :)