diff --git a/src/Calculator/SvgFont.php b/src/Calculator/SvgFont.php
index 662bd8d..8e5044c 100644
--- a/src/Calculator/SvgFont.php
+++ b/src/Calculator/SvgFont.php
@@ -16,25 +16,21 @@
  */
 class SvgFont
 {
-    private const UNICODE_CODE_POINT_M_LOWERCASE = 109;
+    private const DEFAULT_UNITS_PER_EM = 1000;
 
     private array $glyphs;
 
     private int $unitsPerEm;
 
-    private int $glyphSpacingAdvX;
-
     private int $missingGlyphAdvX;
 
     public function __construct(
         array $glyphs = [],
-        int $unitsPerEm = 0,
-        int $glyphSpacingAdvX = 0,
+        int $unitsPerEm = self::DEFAULT_UNITS_PER_EM,
         int $missingGlyphAdvX = 0
     ) {
         $this->glyphs           = $glyphs;
         $this->unitsPerEm       = $unitsPerEm;
-        $this->glyphSpacingAdvX = $glyphSpacingAdvX;
         $this->missingGlyphAdvX = $missingGlyphAdvX;
     }
 
@@ -88,10 +84,6 @@ public static function fromFile(
                         }
 
                         $glyphs[$codePoint]->d = $xml->getAttribute('d');
-
-                        if (self::UNICODE_CODE_POINT_M_LOWERCASE === $codePoint) {
-                            $glyphSpacingHorizAdvX = $glyphs[$codePoint]->horizAdvX;
-                        }
                     }
                 }
             }
@@ -99,8 +91,7 @@ public static function fromFile(
 
         return new self(
             $glyphs,
-            $unitsPerEm ?? 0,
-            $glyphSpacingHorizAdvX ?? 0,
+            $unitsPerEm ?? self::DEFAULT_UNITS_PER_EM,
             $missingGlyphHorizAdvX ?? 0,
         );
     }
@@ -115,7 +106,7 @@ public function computeWidth(
         $glyphAdvX = $this->getGlyphAdvX($codePoint);
 
         $glyphWidth        = $glyphAdvX * $size;
-        $glyphSpacingWidth = $this->glyphSpacingAdvX * $glyphSpacing * $size;
+        $glyphSpacingWidth = $this->unitsPerEm * $glyphSpacing * $size;
 
         return $glyphWidth + $glyphSpacingWidth;
     }