diff --git a/README.md b/README.md
index 5ac25bd..4680df5 100644
--- a/README.md
+++ b/README.md
@@ -77,12 +77,13 @@ Style::setBorderDiagonalDown(style, color)
 ```
 
 ### Cell autosizing
-#### ... is cool, but comes with serious performance impacts!
-| Impacts of autosizing    | 100k rows * 10 cols * 5 chars | 100k rows * 10 cols * 10 chars | 100k rows * 10 cols * 20 chars | 100k rows * 10 cols * 40 chars |
-| ------------------------ | ----------------------------- | ------------------------------ | ------------------------------ | ------------------------------ |
-| Autosizing DISABLED      | 22 seconds                    | 22 seconds                     | 23 seconds                     | 24 seconds                     |
-| Autosizing ENABLED       | 30 seconds                    | 34 seconds                     | 40 seconds                     | 53 seconds                     |
-| Performance loss in %    | + 36 %                        | + 54 %                         | + 73 %                         | + 112 %                        |
+#### ... is cool, but it comes with serious performance impacts, especially when dealing with multibyte characters (like ä, ß, Æ, ポ).
+| Impacts of autosizing                 | 100k rows * 10 cols * 5 chars | 100k rows * 10 cols * 10 chars | 100k rows * 10 cols * 20 chars | 100k rows * 10 cols * 40 chars |
+| ------------------------------------- | ----------------------------- | ------------------------------ | ------------------------------ | ------------------------------ |
+| Autosizing OFF (Single Byte Chars)    | 24 seconds                    | 24 seconds                     | 24 seconds                     | 26 seconds                     |
+| Autosizing ON  (Single Byte Chars)    | 30 seconds (+ 25 %)           | 32 seconds (+ 33 %)            | 35 seconds (+ 45 %)            | 43 seconds (+ 65 %)            |
+| Autosizing OFF (Multi Byte Chars)     | 27 seconds                    | 28 seconds                     | 30 seconds                     | 31 seconds                     |
+| Autosizing ON  (Multi Byte Chars)     | 36 seconds (+ 33 %)           | 41 seconds (+ 46 %)            | 49 seconds (+ 63 %)            | 64 seconds (+ 106 %)           |
 
 ### Additional examples
 ```php
diff --git a/src/OneSheet/Width/WidthCalculator.php b/src/OneSheet/Width/WidthCalculator.php
index 66624d5..4a505f1 100644
--- a/src/OneSheet/Width/WidthCalculator.php
+++ b/src/OneSheet/Width/WidthCalculator.php
@@ -42,7 +42,8 @@ public function __construct(WidthCollection $widthCollection)
     public function getCellWidth($value, Font $font)
     {
         $width = 0.07 * $font->getSize();
-        foreach (preg_split('~~u', $value, -1, PREG_SPLIT_NO_EMPTY) as $character) {
+
+        foreach ($this->getSingleCharacterArray($value) as $character) {
             if (isset($this->characterWidths[$character])) {
                 $width += $this->characterWidths[$character];
             } elseif (strlen($character)) {
@@ -62,4 +63,18 @@ public function setFont(Font $font)
     {
         $this->characterWidths = $this->widthCollection->get($font->getName(), $font->getSize());
     }
+
+    /**
+     * Split value into individual characters.
+     *
+     * @param mixed $value
+     * @return array
+     */
+    private function getSingleCharacterArray($value)
+    {
+        if (mb_strlen($value) == strlen($value)) {
+            return str_split($value);
+        }
+        return preg_split('~~u', $value, -1, PREG_SPLIT_NO_EMPTY);
+    }
 }