diff --git a/src/calculator.py b/src/calculator.py
index 69ae964..6fe859f 100644
--- a/src/calculator.py
+++ b/src/calculator.py
@@ -1,6 +1,6 @@
 # retoor <retoor@molodetz.nl>
 
-from typing import Sequence
+from typing import Sequence, Union
 
 
 def add(left: int, right: int) -> int:
@@ -32,3 +32,10 @@ def variance(values: Sequence[float]) -> float:
     return sum((x - mean) ** 2 for x in values) / len(values)
 
 
+def percentage(value: Union[int, float], total: Union[int, float]) -> float:
+    if total == 0:
+        raise ValueError
+    return (value / total) * 100
+
+
+
diff --git a/tests/test_calculator.py b/tests/test_calculator.py
index 21de386..86d3387 100644
--- a/tests/test_calculator.py
+++ b/tests/test_calculator.py
@@ -3,7 +3,7 @@
 import math
 import unittest
 
-from src.calculator import clamp, variance
+from src.calculator import clamp, percentage, variance
 
 
 class TestClampFunction(unittest.TestCase):
@@ -63,6 +63,31 @@ class TestClampFunction(unittest.TestCase):
         self.assertTrue(math.isnan(result))
 
 
+class TestPercentageFunction(unittest.TestCase):
+
+    def test_valid_percentage(self) -> None:
+        self.assertEqual(percentage(50, 200), 25.0)
+
+    def test_zero_value(self) -> None:
+        self.assertEqual(percentage(0, 100), 0.0)
+
+    def test_full_value(self) -> None:
+        self.assertEqual(percentage(200, 100), 200.0)
+
+    def test_fractional(self) -> None:
+        self.assertAlmostEqual(percentage(1, 3), 33.333333333333336)
+
+    def test_total_zero(self) -> None:
+        with self.assertRaises(ValueError):
+            percentage(50, 0)
+
+    def test_float_arguments(self) -> None:
+        self.assertEqual(percentage(25.5, 100.0), 25.5)
+
+    def test_negative_value(self) -> None:
+        self.assertEqual(percentage(-50, 200), -25.0)
+
+
 class TestVarianceFunction(unittest.TestCase):
 
     def test_empty_list_raises_value_error(self) -> None:
@@ -94,3 +119,4 @@ class TestVarianceFunction(unittest.TestCase):
         self.assertEqual(variance((1, 2, 3, 4, 5)), 2.0)
 
 
+