less mixin to convert px to em/percent step-5

mixin-convert-px-to-em-percent-step-5

#convert-px {
    .calc(@px; @context; @multiply) {
        @ret-convert-px:(@px/@context)*@multiply;
    }
    .em(@tag; @px; @context) {
        .calc(@px, @context, 1);
        .apply(@tag) {
            @{tag}: @ret-convert-px + 0em;
        }
        .apply(@tag);
    }
    .percent(@tag; @px; @context) {
        .calc(@px, @context, 100);
        .apply(@tag) {
            @{tag}: @ret-convert-px + 0%;
        }
        .apply(@tag);
    }
}

gist from blog post