diff --git a/src/UnitConverter/Calculator/AbstractCalculator.php b/src/UnitConverter/Calculator/AbstractCalculator.php
index 9f35d1b8..261b6e48 100644
--- a/src/UnitConverter/Calculator/AbstractCalculator.php
+++ b/src/UnitConverter/Calculator/AbstractCalculator.php
@@ -24,6 +24,36 @@
  */
 abstract class AbstractCalculator implements CalculatorInterface
 {
+    /**
+     * @const int DEFAULT_PRECISION The default precision value.
+     */
+    const DEFAULT_PRECISION = 2;
+
+    /**
+     * @const int DEFAULT_ROUNDING_MODE The default rounding mode for calculators.
+     */
+    const DEFAULT_ROUNDING_MODE = self::ROUND_HALF_UP;
+
+    /**
+     * @const int ROUND_HALF_UP Makes 1.5 into 2 and -1.5 into -2.
+     */
+    const ROUND_HALF_UP = PHP_ROUND_HALF_UP;
+
+    /**
+     * @const int ROUND_HALF_DOWN Makes 1.5 into 1 and -1.5 into -1.
+     */
+    const ROUND_HALF_DOWN = PHP_ROUND_HALF_DOWN;
+
+    /**
+     * @const int ROUND_HALF_EVEN Rounds to the nearest even value.
+     */
+    const ROUND_HALF_EVEN = PHP_ROUND_HALF_EVEN;
+
+    /**
+     * @const int ROUND_HALF_ODD Rounds to the nearest odd value.
+     */
+    const ROUND_HALF_ODD = PHP_ROUND_HALF_ODD;
+
     /**
      * @var int $precision The number of decimal places that will calculated
      */
@@ -45,8 +75,8 @@ abstract class AbstractCalculator implements CalculatorInterface
      */
     public function __construct (int $precision = null, int $roundingMode = null)
     {
-        $this->setPrecision(($precision ?? 2));
-        $this->setRoundingMode(($roundingMode ?? PHP_ROUND_HALF_UP));
+        $this->setPrecision(($precision ?? self::DEFAULT_PRECISION));
+        $this->setRoundingMode(($roundingMode ?? self::DEFAULT_ROUNDING_MODE));
     }
 
     public function setPrecision (int $precision): CalculatorInterface