diff --git a/src/AbService.php b/src/AbService.php
index 06d3879..633c011 100644
--- a/src/AbService.php
+++ b/src/AbService.php
@@ -109,10 +109,10 @@ public function getVariant(string $experiment): string
 
     public function getHash(string $uid, string $experiment): float
     {
-        $hex = substr(hash('sha256', $uid . $experiment), 0, 16);
+        $hex = substr(hash('sha256', $uid . $experiment), 0, 15);
         $int = hexdec($hex);
 
-        return $int / 0xFFFFFFFFFFFFFFFF;
+        return $int / 2 ** 60;
     }
 
     public function chooseVariant(float $hash, array $variants): string
@@ -122,8 +122,9 @@ public function chooseVariant(float $hash, array $variants): string
 
         $names = array_keys($variants);
         $weights = array_values($variants);
+        $nameCount = count($names);
 
-        for ($i = 0; $i < count($names) -1; $i++) {
+        for ($i = 0; $i < $nameCount - 1; $i++) {
             $sum += $weights[$i];
 
             if ($hash < $sum) {
diff --git a/test/AbServiceTest.php b/test/AbServiceTest.php
index ea08883..52bd2a8 100644
--- a/test/AbServiceTest.php
+++ b/test/AbServiceTest.php
@@ -96,7 +96,7 @@ public function testGetVariant(): void
     public function testGetVariantDistributed(): void
     {
         $this->markTestSkipped("takes a while");
-        
+
         $iterations = 1000000;
         $delta = $iterations / 500; // 0.2% difference