diff --git a/src/Tiebreaks.php b/src/Tiebreaks.php
index 5f07958..19259a3 100644
--- a/src/Tiebreaks.php
+++ b/src/Tiebreaks.php
@@ -153,7 +153,7 @@ abstract class Tiebreaks extends Tournament
     protected function calculateKoya(Player $player, int $cut = 50)
     {
         $tiebreak = 0;
-        foreach ($player->getPairings() as $plkey=>$plpairing) {
+        foreach ($player->getPairings() as $plkey => $plpairing) {
             if (($plpairing->getOpponent()->getNoOfWins() / count($plpairing->getOpponent()->getPairings()) * 100) >= $cut) {
                 $tiebreak += $plpairing->getOpponent()->getNoOfWins();
             }
@@ -183,9 +183,27 @@ abstract class Tiebreaks extends Tournament
         array_splice($intpairings, $cutlowest);
         array_splice($intpairings, 0 - $cuthighest);
 
-        foreach ($intpairings as $intkey=>$intpairing) {
+        foreach ($intpairings as $intkey => $intpairing) {
             $tiebreak += $intpairing->getOpponent()->getPoints();
         }
         return $tiebreak;
     }
+
+
+    /**
+     * @param Player $player
+     * @return float|int|null
+     */
+    protected function calculateSonneborn(Player $player)
+    {
+        $tiebreak = 0;
+        foreach ($player->getPairings() as $key => $pairing) {
+            if (array_search($pairing->getResult(), Constants::Won) !== false) {
+                $tiebreak += $pairing->getOpponent()->getPoints();
+            } elseif (array_search($pairing->getResult(), Constants::draw) !== false) {
+                $tiebreak += $pairing->getOpponent()->getPoints() / 2;
+            }
+        }
+        return $tiebreak;
+    }
 }
diff --git a/src/Tournament.php b/src/Tournament.php
index bd735b4..0d468af 100644
--- a/src/Tournament.php
+++ b/src/Tournament.php
@@ -308,6 +308,9 @@ class Tournament extends Tiebreaks
             case Tiebreak::BuchholzMed:
                 return $this->calculateBuchholz($player, 1, 1);
                 break;
+            case Tiebreak::Sonneborn:
+                return $this->calculateSonneborn($player);
+                break;
             default:
                 return null;
         }