diff --git a/predict.py b/predict.py
index bf64120..6436f1a 100644
--- a/predict.py
+++ b/predict.py
@@ -1,5 +1,5 @@
 import errno
-from argparse import ArgumentParser
+from argparse import ArgumentParser, ArgumentTypeError
 from pathlib import Path
 
 import torch
@@ -21,6 +21,12 @@
         required=True,
         help='the path to the model weight'
     )
+    parser.add_argument(
+        '--scale',
+        type=float,
+        default=1.0,
+        help='adjust the scaling ratio. default to 1.0.'
+    )
     parser.add_argument(
         '--save-annotated',
         type=str,
@@ -33,6 +39,9 @@
     )
     args = parser.parse_args()
 
+    if args.scale <= 0.0:
+        raise ArgumentTypeError(message='scale must be greater than 0.0')
+
     if args.save_annotated is not None:
         save_annotated = Path(args.save_annotated)
         if not save_annotated.is_dir():
@@ -59,7 +68,7 @@
 
     streamer = ImageStreamer(args.source)
     for i, image in enumerate(streamer):
-        prediction = predictor.predict(image)
+        prediction = predictor.predict(image, scaling_ratio=args.scale)
 
         print(f'Prediction #{i}')
         print('  bounds', prediction.bounds.tolist())
diff --git a/wpodnet/backend.py b/wpodnet/backend.py
index 1c61e69..6eabce5 100644
--- a/wpodnet/backend.py
+++ b/wpodnet/backend.py
@@ -81,7 +81,7 @@ def _inference(self, image: torch.Tensor) -> Tuple[np.ndarray, np.ndarray]:
     def _get_max_anchor(self, probs: np.ndarray) -> Tuple[int, int]:
         return np.unravel_index(probs.argmax(), probs.shape)
 
-    def _get_bounds(self, affines: np.ndarray, anchor_y: int, anchor_x: int) -> np.ndarray:
+    def _get_bounds(self, affines: np.ndarray, anchor_y: int, anchor_x: int, scaling_ratio: float = 1.0) -> np.ndarray:
         # Compute theta
         theta = affines[:, anchor_y, anchor_x]
         theta = theta.reshape((2, 3))
@@ -89,7 +89,7 @@ def _get_bounds(self, affines: np.ndarray, anchor_y: int, anchor_x: int) -> np.n
         theta[1, 1] = max(theta[1, 1], 0.0)
 
         # Convert theta into the bounding polygon
-        bounds = np.matmul(theta, self._q) * self._scaling_const
+        bounds = np.matmul(theta, self._q) * self._scaling_const * scaling_ratio
 
         # Normalize the bounds
         _, grid_h, grid_w = affines.shape
@@ -98,7 +98,7 @@ def _get_bounds(self, affines: np.ndarray, anchor_y: int, anchor_x: int) -> np.n
 
         return np.transpose(bounds)
 
-    def predict(self, image: Image.Image) -> Prediction:
+    def predict(self, image: Image.Image, scaling_ratio: float = 1.0) -> Prediction:
         orig_h, orig_w = image.height, image.width
 
         # Resize the image to fixed ratio
@@ -115,7 +115,7 @@ def predict(self, image: Image.Image) -> Prediction:
         # Get the theta with maximum probability
         max_prob = np.amax(probs)
         anchor_y, anchor_x = self._get_max_anchor(probs)
-        bounds = self._get_bounds(affines, anchor_y, anchor_x)
+        bounds = self._get_bounds(affines, anchor_y, anchor_x, scaling_ratio)
 
         bounds[:, 0] *= orig_w
         bounds[:, 1] *= orig_h