diff --git a/calculator.py b/calculator.py
new file mode 100644
index 0000000..850faf7
--- /dev/null
+++ b/calculator.py
@@ -0,0 +1,87 @@
+#!/usr/bin/env python3
+"""Simple CLI calculator.
+
+Usage:
+  python calculator.py add 2 3
+  python calculator.py subtract 5 2
+  python calculator.py multiply 4 6
+  python calculator.py divide 10 2
+
+Output is the numeric result. If the result is an integer, it is printed as an int
+without a trailing decimal point.
+"""
+
+import sys
+
+
+def _to_number(s: str) -> float:
+    # Always parse as float for flexibility, callers will format as int when appropriate
+    try:
+        return float(s)
+    except ValueError as exc:
+        raise TypeError(f"Invalid number: {s}") from exc
+
+
+def add(a: float, b: float) -> float:
+    return a + b
+
+
+def subtract(a: float, b: float) -> float:
+    return a - b
+
+
+def multiply(a: float, b: float) -> float:
+    return a * b
+
+
+def divide(a: float, b: float) -> float:
+    if b == 0:
+        raise ZeroDivisionError("division by zero")
+    return a / b
+
+
+def _format_result(value: float) -> str:
+    # If the value is an integer, print as int for nicer output
+    if value.is_integer():
+        return str(int(value))
+    return str(value)
+
+
+def main(argv: list[str]) -> int:
+    if len(argv) != 4:
+        print("Usage: python calculator.py <operation> <a> <b>")
+        return 2
+
+    op, sa, sb = argv[1], argv[2], argv[3]
+
+    try:
+        a = _to_number(sa)
+        b = _to_number(sb)
+    except TypeError as exc:
+        print(str(exc))
+        return 2
+
+    try:
+        if op == "add":
+            res = add(a, b)
+        elif op == "subtract":
+            res = subtract(a, b)
+        elif op == "multiply":
+            res = multiply(a, b)
+        elif op == "divide":
+            res = divide(a, b)
+        else:
+            print(f"Unknown operation: {op}")
+            return 2
+    except ZeroDivisionError as exc:
+        print(str(exc))
+        return 1
+
+    # Print formatted result
+    print(_format_result(res))
+    return 0
+
+
+if __name__ == "__main__":
+    # Support direct execution from the repository root
+    raise SystemExit(main(sys.argv))