diff --git a/maths/number_of_digits.py b/maths/number_of_digits.py
new file mode 100644
index 000000000..127170651
--- /dev/null
+++ b/maths/number_of_digits.py
@@ -0,0 +1,18 @@
+def num_digits(n: int) -> int:
+    """
+    Find the number of digits in a number.
+
+    >>> num_digits(12345)
+    5
+    >>> num_digits(123)
+    3
+    """
+    digits = 0
+    while n > 0:
+        n = n // 10
+        digits += 1
+    return digits
+
+
+if __name__ == "__main__":
+    print(num_digits(12345))   # ===> 5