diff --git a/src/main/res/raw/ops.forth b/src/main/res/raw/ops.forth
index 081791f..2cd0c69 100644
--- a/src/main/res/raw/ops.forth
+++ b/src/main/res/raw/ops.forth
@@ -99,4 +99,5 @@
 : day ( -- y )
     :java.util.Calendar/DAY_OF_MONTH jvm-static-var
     :java.util.Calendar/getInstance jvm-call-static
-    :get/i jvm-call-method ;
\ No newline at end of file
+    :get/i jvm-call-method ;
+: d% ( n1 n2 -- n3 ) swap dup abs >r - r> / 100 * ;
diff --git a/src/test/java/com/vectron/fcl/FclTest.java b/src/test/java/com/vectron/fcl/FclTest.java
index 444069f..4830fea 100644
--- a/src/test/java/com/vectron/fcl/FclTest.java
+++ b/src/test/java/com/vectron/fcl/FclTest.java
@@ -400,7 +400,12 @@ public class FclTest {
         assertEquals(10, evalPop("100 10 percent").doubleValue(), 0.001);
         assertEquals(100, evalPop("100 100 percent").doubleValue(), 0.001);
         assertEquals(130.686, evalPop("4356.2 3 percent").doubleValue(), 0.001);
-        assertEquals(0.16482, evalPop("1.23 13.4 percent").doubleValue(), 0.001);
+        assertEquals(10, evalPop("100 110 d%").doubleValue(), 0.001);
+        assertEquals(-10, evalPop("100 90 d%").doubleValue(), 0.001);
+        assertEquals(181.026, evalPop("23.4 65.76 d%").doubleValue(), 0.001);
+        assertEquals(-181.026, evalPop("-23.4 -65.76 d%").doubleValue(), 0.001);
+        assertEquals(-381.026, evalPop("23.4 -65.76 d%").doubleValue(), 0.001);
+        assertEquals(381.026, evalPop("-23.4 65.76 d%").doubleValue(), 0.001);
     }
 
     @Test