diff --git a/framework/CHANGELOG.md b/framework/CHANGELOG.md
index fb3137578b..ca871c8e2d 100644
--- a/framework/CHANGELOG.md
+++ b/framework/CHANGELOG.md
@@ -71,6 +71,7 @@ Yii Framework 2 Change Log
 - Bug #4342: mssql (dblib) driver does not support getting attributes (tof06)
 - Bug #4409: Upper case letters in subdirectory prefixes of controller IDs were not properly handled (qiangxue)
 - Bug #4412: Formatter used SI Prefixes for base 1024, now uses binary prefixes (kmindi)
+- Bug #4427: Formatter could do one division too much (kmindi)
 - Bug: Fixed inconsistent return of `\yii\console\Application::runAction()` (samdark)
 - Bug: URL encoding for the route parameter added to `\yii\web\UrlManager` (klimov-paul)
 - Bug: Fixed the bug that requesting protected or private action methods would cause 500 error instead of 404 (qiangxue)
diff --git a/framework/base/Formatter.php b/framework/base/Formatter.php
index e2839dbfe9..1fe60378ac 100644
--- a/framework/base/Formatter.php
+++ b/framework/base/Formatter.php
@@ -461,7 +461,7 @@ class Formatter extends Component
 
             $value = $value / $this->sizeFormat['base'];
             $position++;
-        } while ($position < 6);
+        } while ($position < 5);
 
         $value = round($value, $this->sizeFormat['decimals']);
         $formattedValue = isset($this->sizeFormat['decimalSeparator']) ? str_replace('.', $this->sizeFormat['decimalSeparator'], $value) : $value;
diff --git a/tests/unit/framework/base/FormatterTest.php b/tests/unit/framework/base/FormatterTest.php
index ecc201fae7..1643b8eacf 100644
--- a/tests/unit/framework/base/FormatterTest.php
+++ b/tests/unit/framework/base/FormatterTest.php
@@ -193,11 +193,13 @@ class FormatterTest extends TestCase
     public function testAsSize() {
         // tests for base 1000
         $this->formatter->sizeFormat['base'] = 1000;
+        $this->assertSame("999 B", $this->formatter->asSize(999));
         $this->assertSame("1.05 MB", $this->formatter->asSize(1024 * 1024));
         $this->assertSame("1.05 MB", $this->formatter->asSize(1024 * 1024, false, false));
         $this->assertSame("1 KB", $this->formatter->asSize(1000));
         $this->assertSame("1.02 KB", $this->formatter->asSize(1023));
         $this->assertSame("3 gigabytes", $this->formatter->asSize(3 * 1000 * 1000 * 1000, true));
+        $this->assertNotSame("3 PB", $this->formatter->asSize(3 * 1000 * 1000 * 1000 * 1000 * 1000 * 1000)); // this is 3 EB not 3 PB
         
         // tests for base 1024
         $this->formatter->sizeFormat['base'] = 1024;
@@ -205,6 +207,8 @@ class FormatterTest extends TestCase
         $this->assertSame("1 MB", $this->formatter->asSize(1024 * 1024, false, false));
         $this->assertSame("1023 B", $this->formatter->asSize(1023));
         $this->assertSame("5 GiB", $this->formatter->asSize(5 * 1024 * 1024 * 1024));
+        $this->assertSame("5 gibibytes", $this->formatter->asSize(5 * 1024 * 1024 * 1024,true));
+        $this->assertNotSame("5 PiB", $this->formatter->asSize(5 * 1024 * 1024 * 1024 * 1024 * 1024 * 1024)); // this is 5 EiB not 5 PiB
         //$this->assertSame("1 YiB", $this->formatter->asSize(pow(2, 80)));
         $this->assertSame("2 GiB", $this->formatter->asSize(2147483647)); // round 1.999 up to 2
         $this->formatter->sizeFormat['decimalSeparator'] = ',';