size: P / 15
height: 19 / P
margin: Q / P

h1: 24px
h2: 14px

h1: 
   size: 24 / 15 = 1.6em
   height: 19 / 24 = 0.79167em
   margin: @@

h2: 
   size: 14 / 15 = 0.9333em
   height: 19 / 14 = 1.3571em
   margin: @@

p: 
   size: 1em
   line-height: 19 / 15 = 1.2667em

h2: 
   size: 13 / 15 = 0.8667em
   height: 19 / 13 = 1.4615em
   margin-top: 27 / 13 = 2.0769em
   margin-bottom: 9 / 13 = 0.6923em

   size: 12 / 15 = 0.8em
   height: 19 / 12 = 1.5833em
   margin-top: 27 / 12 = 2.25em
   margin-bottom: 9 / 12 = 0.75em

h2 { 
   font-family: "Lucida Grande", Helvetica, sans-serif; 
   font-weight: bold; 
   font-size: 0.8em; 
   line-height: 1.5833em; 
   margin-top: 2.25em; 
   margin-bottom: 0.75em; 
}

   font-size: 0.9333em;
   line-height: 1.3571em;
   margin-top: 1.929em;
   margin-bottom: 0.643em;

h1: 
   size: 25 / 15 = 1.6667em
   height: 19 / 25 = 0.76em
   margin: @@

   font-size: 1.6em;
   line-height: 0.79167em;
   margin: 0 0 1.6em 0;

1.6 * 15

32 / 25