diff --git a/maths/sum_of_digits.py b/maths/sum_of_digits.py
new file mode 100644
index 000000000..88baf2ca2
--- /dev/null
+++ b/maths/sum_of_digits.py
@@ -0,0 +1,18 @@
+def sum_of_digits(n: int) -> int:
+    """
+    Find the sum of digits of a number.
+
+    >>> sum_of_digits(12345)
+    15
+    >>> sum_of_digits(123)
+    6
+    """
+    res = 0
+    while n > 0:
+        res += n % 10
+        n = n // 10
+    return res
+
+
+if __name__ == "__main__":
+    print(sum_of_digits(12345))  # ===> 15