diff --git a/scripts/s3_stats.py b/scripts/s3_stats.py
new file mode 100644
index 0000000..4797bcd
--- /dev/null
+++ b/scripts/s3_stats.py
@@ -0,0 +1,71 @@
+import sys
+
+
+def main() -> None:
+    """Process S3 stats from an input file given as the first CLI argument."""
+
+    if len(sys.argv) < 2:
+        print(f"Usage: {sys.argv[0]} <input_file>")
+        sys.exit(1)
+
+    input_file = sys.argv[1]
+
+    # generate the input file with:
+    # aws --endpoint-url https://uk1s3.embassy.ebi.ac.uk s3 ls --summarize --recursive --no-sign-request bia-idr-integration/S-BIAD1891 > idr0168_du.txt
+    #
+    # example input lines:
+    # 2025-08-11 00:57:36      35255 S-BIAD2216/microglia_zipped/HC/caudate/HC10/Patient_ImageStack_0008.ome.zarr/3/0/22/0/0
+    # 2025-08-11 00:57:36      35246 S-BIAD2216/microglia_zipped/HC/caudate/HC10/Patient_ImageStack_0008.ome.zarr/3/0/23/0/0
+    # 2025-08-11 00:57:37      35245 S-BIAD2216/microglia_zipped/HC/caudate/HC10/Patient_ImageStack_0008.ome.zarr/3/0/24/0/0
+    # 2025-08-11 00:57:37      35233 S-BIAD2216/microglia_zipped/HC/caudate/HC10/Patient_ImageStack_0008.ome.zarr/3/0/3/0/0
+
+    # summarize number of bytes (2nd numeric column) per ome.zarr (derived from path)
+    totals: dict[str, int] = {}
+
+    with open(input_file) as f:
+        for line in f:
+            line = line.strip()
+            if not line:
+                continue
+
+            parts = line.split()
+            # Expect at least: date, time, size, path
+            if len(parts) < 4:
+                continue
+
+            try:
+                size = int(parts[2])
+            except ValueError:
+                continue
+
+            # Path may be in parts[3], additional whitespace already collapsed by split()
+            path = parts[3]
+
+            # Trim to the ome.zarr root
+            marker = ".zarr"
+            idx = path.find(marker)
+            if idx == -1:
+                # Not an ome.zarr path
+                continue
+
+            ome_zarr = path[: idx + len(marker)]
+
+            totals[ome_zarr] = totals.get(ome_zarr, 0) + size
+
+    # Print summary sorted by ome.zarr path
+    for ome_zarr in sorted(totals):
+        print(totals[ome_zarr], ome_zarr)
+
+    # Print overall stats
+    if totals:
+        num_ome_zarrs = len(totals)
+        total_bytes = sum(totals.values())
+        avg_bytes = total_bytes / num_ome_zarrs
+        print()
+        print(f"# ome.zarrs: {num_ome_zarrs}")
+        print(f"total bytes: {total_bytes}")
+        print(f"avg bytes / ome.zarr: {avg_bytes}")
+
+
+if __name__ == "__main__":
+    main()