Showing the expected output of the rem mixin

rem-results

I'm trying to do this:

html{
  font-size:62.5%;
}

body{
  @include rem(font-size, 14px);
  line-height:1.6;
}

But I believe the rem mixin gives me this with the following:
$browser-default-font-size: 16px; // Is this right?
$base-font-size: 10px !default; // Is this right?

html{
  font-size:62.5%;
}

body{
  font-size: 14px;
  font-size: .875rem;
}

I was expecting the following:

html{
  font-size:62.5%;
}

body{
  font-size: 14px;
  font-size: 1.4rem;
}

I suspect the $base-font-size variable is not being set with the correct value. The mixin's $base-font-size is a configurable variable. You should set it in your own stylesheet before importing the mixin.

$base-font-size: 10px; // This is what determines the pixel value of 1rem for the mixin
@import "rem";  // path to the rem mixin

html {
  font-size: 62.5%;
}

body {
  @include rem(font-size, 14px);
}

Should compile to:

html {
  font-size: 62.5%;
}

body {
  font-size: 14px;
  font-size: 1.4rem;  /* 14px/10px = 1.4 */
}

However, since you are using mixins to help size your text, you don't really need the 62.5% technique to give you a round number to work from. It seems that your real desired base font-size is 14px. Sass gives us the power to set it that way!

$base-font-size: 14px;
@import "rem";

html {
  font-size: $base-font-size/$browser-default-font-size * 100%; // 14px/16px * 100% = 87.5%
}

body {
  // you don't need to set anything: will inherit the font-size of html, which computes to 14px
}

// example
h1 {
  @include rem(font-size, 24px);  // will compile to 24px and 1.71428rem (24px/14px = 1.71428)
}

By the way you should also check out the Compass vertical rhythm module. It's great for working with type sizing and spacing even if you're not a strict proponent of baseline grids on the web. The master branch (not yet released) will support rems and pixel fallbacks.