diff --git a/src/Rule/ContainsLowercaseCharacters.php b/src/Rule/ContainsLowercaseCharacters.php
new file mode 100644
index 0000000..b5859de
--- /dev/null
+++ b/src/Rule/ContainsLowercaseCharacters.php
@@ -0,0 +1,83 @@
+<?php
+
+namespace Morebec\Validator\Rule;
+
+
+use InvalidArgumentException;
+use Morebec\Validator\ValidationRuleInterface;
+
+class ContainsLowercaseCharacters implements ValidationRuleInterface
+{
+    /**
+     * @var int
+     */
+    private $numberCharacters;
+
+    /**
+     * @var bool
+     */
+    private $strict;
+
+    /**
+     * @var string|null
+     */
+    private $message;
+
+    /**
+     * ContainsLowercaseCharacters constructor.
+     * @param int $numberCharacters
+     * @param bool $strict
+     * @param string|null $message
+     */
+    public function __construct(
+        int $numberCharacters,
+        bool $strict,
+        ?string $message = null
+    )
+    {
+        if($numberCharacters<0)
+            throw new InvalidArgumentException();
+        $this->numberCharacters = $numberCharacters;
+        $this->strict = $strict;
+        $this->message = $message;
+    }
+
+    /**
+     * Validates a value according to this rule and returns if it is valid or not
+     * @param mixed $v
+     * @return bool true if valid, otherwise false
+     */
+    public function validate($v): bool
+    {
+        if($this->strict){
+            return $this->countLowerCase($v)<=$this->numberCharacters;
+        }
+        return $this->countLowerCase($v)>=$this->numberCharacters;
+    }
+
+    /**
+     * Returns the message to be used in case the validation did not pass
+     * @param mixed $v the value that did not pass the validation
+     * @return string
+     */
+    public function getMessage($v): string
+    {
+        if($this->message){
+            return $this->message;
+        }
+        if($this->strict){
+            return "Number of lowercase characters exceeds ".${$this->numberCharacters};
+        }
+        return "Number of lowercase characters should exceed ".${$this->numberCharacters};
+    }
+
+    /**
+     * @param string $message
+     * @return int
+     */
+    private function countLowerCase(string $message) :int {
+        $upperCase = strtoupper($message);
+        $similar = similar_text($message,$upperCase);
+        return strlen($message)-$similar;
+    }
+}
\ No newline at end of file
diff --git a/tests/Rule/ContainsLowercaseCharactersTest.php b/tests/Rule/ContainsLowercaseCharactersTest.php
new file mode 100644
index 0000000..0728469
--- /dev/null
+++ b/tests/Rule/ContainsLowercaseCharactersTest.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace Tests\Morebec\Validator\Rule;
+use InvalidArgumentException;
+use Morebec\Validator\Rule\ContainsLowercaseCharacters;
+use PHPUnit\Framework\TestCase;
+
+
+class ContainsLowercaseCharactersTest extends TestCase
+{
+    public function testValidate(){
+        $ruleFirst = new ContainsLowercaseCharacters(1,true);
+        $ruleSecond = new ContainsLowercaseCharacters(1,false);
+        $ruleThird= new ContainsLowercaseCharacters(1,false,"Custom Message");
+        $this->assertTrue($ruleFirst->validate("tEST STRING"));
+        $this->assertFalse($ruleFirst->validate("tEST sTRING"));
+        $this->assertFalse($ruleSecond->validate('TEST STRING'));
+        $this->assertTrue($ruleSecond->validate('tEST sTRING'));
+        $this->assertEquals( "Custom Message", $ruleThird->getMessage("test string"));
+        $this->expectException(InvalidArgumentException::class);
+        $ruleFourth = new ContainsLowercaseCharacters(-1,false);
+    }
+}
\ No newline at end of file