diff --git a/src/twomartens/masterthesis/cli.py b/src/twomartens/masterthesis/cli.py
index b70ec51..79a9061 100644
--- a/src/twomartens/masterthesis/cli.py
+++ b/src/twomartens/masterthesis/cli.py
@@ -399,3 +399,25 @@ def visualise(args: argparse.Namespace) -> None:
             pyplot.close(figure)
         
         i += 1
+
+
+def measure_mapping(args: argparse.Namespace) -> None:
+    import pickle
+
+    from twomartens.masterthesis.ssd_keras.eval_utils import coco_utils
+
+    with open(f"{args.ground_truth_path}/instances.bin", "rb") as file:
+        instances = pickle.load(file)
+
+    output_path = f"{args.output_path}/measure/{args.tarball_id}"
+    annotation_file_train = f"{args.coco_path}/annotations/instances_train2014.json"
+    cats_to_classes, _, _, _ = coco_utils.get_coco_category_maps(annotation_file_train)
+    
+    for i, trajectory in enumerate(instances):
+        counts = {cat_id: 0 for cat_id in cats_to_classes.keys()}
+        for labels in trajectory:
+            for instance in labels:
+                counts[instance['coco_id']] += 1
+        
+        with open(f"{output_path}/{i}.bin", "wb") as file:
+            pickle.dump(counts, file)
diff --git a/src/twomartens/masterthesis/main.py b/src/twomartens/masterthesis/main.py
index 8d1ec06..8164f60 100644
--- a/src/twomartens/masterthesis/main.py
+++ b/src/twomartens/masterthesis/main.py
@@ -44,6 +44,7 @@ def main() -> None:
     evaluate_parser = sub_parsers.add_parser("evaluate", help="Evaluate a network")
     test_parser = sub_parsers.add_parser("test", help="Test a network")
     visualise_parser = sub_parsers.add_parser("visualise", help="Visualise the ground truth")
+    measure_parser = sub_parsers.add_parser("measure_mapping", help="Measure the number of instances per COCO category")
     
     # build sub parsers
     _build_prepare(prepare_parser)
@@ -51,6 +52,7 @@ def main() -> None:
     _build_test(test_parser)
     _build_evaluate(evaluate_parser)
     _build_visualise(visualise_parser)
+    _build_measure(measure_parser)
     
     args = parser.parse_args()
     
@@ -64,6 +66,8 @@ def main() -> None:
         cli.prepare(args)
     elif args.action == "visualise":
         cli.visualise(args)
+    elif args.action == "measure_mapping":
+        cli.measure_mapping(args)
 
 
 def _build_prepare(parser: argparse.ArgumentParser) -> None:
@@ -166,5 +170,12 @@ def _build_visualise(parser: argparse.ArgumentParser) -> None:
     parser.add_argument("trajectory", type=int, help="trajectory to visualise")
 
 
+def _build_measure(parser: argparse.ArgumentParser) -> None:
+    parser.add_argument("--coco_path", type=str, help="the path to the COCO data set")
+    parser.add_argument("--ground_truth_path", type=str, help="path to the prepared ground truth directory")
+    parser.add_argument("--output_path", type=str, help="path to the output directory")
+    parser.add_argument("tarball_id", type=int, help="id of the used tarball")
+
+
 if __name__ == "__main__":
     main()