diff --git a/lib/canvas.js b/lib/canvas.js
index 065ff6f..741f5fa 100644
--- a/lib/canvas.js
+++ b/lib/canvas.js
@@ -476,6 +476,8 @@ Context2d.prototype.__defineSetter__('font', function(val){
   if ('string' == typeof val) {
     var font;
     if (font = parseFont(val)) {
+      // TODO: cache
+      // TODO: dpi
       this.lastFontString = val;
       
       switch (font.unit) {
@@ -485,6 +487,12 @@ Context2d.prototype.__defineSetter__('font', function(val){
         case 'in':
           font.size *= 96;
           break;
+        case 'mm':
+          font.size *= 96.0 / 25.4;
+          break;
+        case 'cm':
+          font.size *= 96.0 / 2.54;
+          break;
       }
 
       this.setFont(