PX->EM mixin for fonts in LESS

/* Base font, 10px = 1em */
body {
  font-size: 62.5%;
}

/* LESS */
.text-heading (@weight: 500, @size: 26, @line: 34){
    @font-size: @size/10;
    @font-line: (@line/@size);
    font:@weight ~'@{font-size}em'~'/'~'@{font-line}em' Arial,sans-serif;
    text-rendering:optimizeLegibility;
}

/* How to use */

h1 {
    .text-heading(bold,24,36)
}

/* Output */

h1 {
  font: bold 2.4em / 1.5em Arial, sans-serif;
  text-rendering: optimizeLegibility;
}