diff --git a/lib/Cake/Test/Case/Utility/CakeNumberTest.php b/lib/Cake/Test/Case/Utility/CakeNumberTest.php
index 9a28eb8bf..8ebaad5de 100644
--- a/lib/Cake/Test/Case/Utility/CakeNumberTest.php
+++ b/lib/Cake/Test/Case/Utility/CakeNumberTest.php
@@ -642,6 +642,13 @@ class CakeNumberTest extends CakeTestCase {
 			array(array('size' => '1.5MB', 'default' => false), 1572864),
 			array(array('size' => '1GB', 'default' => false), 1073741824),
 			array(array('size' => '1.5GB', 'default' => false), 1610612736),
+			array(array('size' => '1K', 'default' => false), 1024),
+			array(array('size' => '1.5K', 'default' => false), 1536),
+			array(array('size' => '1M', 'default' => false), 1048576),
+			array(array('size' => '1m', 'default' => false), 1048576),
+			array(array('size' => '1.5M', 'default' => false), 1572864),
+			array(array('size' => '1G', 'default' => false), 1073741824),
+			array(array('size' => '1.5G', 'default' => false), 1610612736),
 			array(array('size' => '512', 'default' => 'Unknown type'), 512),
 			array(array('size' => '2VB', 'default' => 'Unknown type'), 'Unknown type')
 		);
diff --git a/lib/Cake/Utility/CakeNumber.php b/lib/Cake/Utility/CakeNumber.php
index 88a96ba33..b02fc562a 100644
--- a/lib/Cake/Utility/CakeNumber.php
+++ b/lib/Cake/Utility/CakeNumber.php
@@ -111,26 +111,31 @@ class CakeNumber {
 /**
  * Converts filesize from human readable string to bytes
  *
- * @param string $size Size in human readable string like '5MB'
+ * @param string $size Size in human readable string like '5MB', '5M', '500B', '50kb' etc.
  * @param mixed $default Value to be returned when invalid size was used, for example 'Unknown type'
- * @return integer Bytes
+ * @return mixed Number of bytes as integer on success, `$default` on failure if not false
  * @throws CakeException On invalid Unit type.
  */
 	public static function fromReadableSize($size, $default = false) {
 		if (ctype_digit($size)) {
-			return $size * 1;
+			return (int)$size;
 		}
 		$size = strtoupper($size);
 
+		$l = -2;
 		$i = array_search(substr($size, -2), array('KB', 'MB', 'GB', 'TB', 'PB'));
+		if ($i === false) {
+			$l = -1;
+			$i = array_search(substr($size, -1), array('K', 'M', 'G', 'T', 'P'));
+		}
 		if ($i !== false) {
-			$size = substr($size, 0, strlen($size) - 2);
+			$size = substr($size, 0, $l);
 			return $size * pow(1024, $i + 1);
 		}
 
-		if (substr($size, -1) == 'B' && ctype_digit(substr($size, 0, strlen($size) - 1))) {
-			$size = substr($size, 0, strlen($size) - 1);
-			return $size * 1;
+		if (substr($size, -1) == 'B' && ctype_digit(substr($size, 0, -1))) {
+			$size = substr($size, 0, -1);
+			return (int)$size;
 		}
 
 		if ($default !== false) {