diff --git a/config/default.yaml b/config/default.yaml
index b6a0cf2..7b9c298 100644
--- a/config/default.yaml
+++ b/config/default.yaml
@@ -76,6 +76,7 @@ face:
   roi_expand_ratio: 0.20
   roi_square: true
   roi_upscale_target: 384
+  roi_truncated_width_ratio: 0.45
   min_roi_width: 40
   min_roi_height: 40
   static_image_mode: false
diff --git a/src/config_loader.py b/src/config_loader.py
index 3e10be0..4d663d7 100644
--- a/src/config_loader.py
+++ b/src/config_loader.py
@@ -183,6 +183,7 @@ class FaceSettings:
     roi_expand_ratio: float
     roi_square: bool
     roi_upscale_target: int
+    roi_truncated_width_ratio: float
     min_roi_width: int
     min_roi_height: int
     static_image_mode: bool
@@ -578,6 +579,8 @@ def _validate(config: AppConfig) -> None:
         raise ConfigurationError("face minimum ROI dimensions must be positive")
     if face.roi_upscale_target < 0 or not isinstance(face.roi_square, bool):
         raise ConfigurationError("face roi_square/roi_upscale_target is invalid")
+    if face.roi_truncated_width_ratio <= 0:
+        raise ConfigurationError("face roi_truncated_width_ratio must be positive")
     if not 0.0 <= face.min_detection_confidence <= 1.0 or not 0.0 <= face.min_tracking_confidence <= 1.0:
         raise ConfigurationError("face confidence thresholds must be in [0, 1]")
     pose = config.head_pose
diff --git a/src/face_geometry.py b/src/face_geometry.py
index 8c3186c..d2f501b 100644
--- a/src/face_geometry.py
+++ b/src/face_geometry.py
@@ -3,8 +3,6 @@
 from .config_loader import FaceSettings
 from .models import FaceROI, TrackedPerson
 
-TRUNCATED_WIDTH_RATIO = 0.45
-
 def create_face_roi(person: TrackedPerson, frame_width: int, frame_height: int, config: FaceSettings) -> FaceROI | None:
     """Create a clipped upper-body ROI or return None when the track is ineligible."""
     if config.require_confirmed_track and not person.is_confirmed:
@@ -14,7 +12,7 @@ def create_face_roi(person: TrackedPerson, frame_width: int, frame_height: int,
     bbox = person.bbox
     candidate_height = bbox.height * config.roi_height_ratio
     if bbox.y2 >= frame_height - 2:
-        candidate_height = max(candidate_height, bbox.width * TRUNCATED_WIDTH_RATIO)
+        candidate_height = max(candidate_height, bbox.width * config.roi_truncated_width_ratio)
     expand_x = bbox.width * config.roi_expand_ratio
     expand_y = candidate_height * config.roi_expand_ratio
     y1 = max(0, round(bbox.y1 - expand_y))