diff --git a/Tools/container_data_export.sh b/Tools/container_data_export.sh
index 50c7756..ef53ae9 100755
--- a/Tools/container_data_export.sh
+++ b/Tools/container_data_export.sh
@@ -144,13 +144,26 @@ if [[ ! -d "$OUTPUT_DIR" ]]; then
 fi
 
 # Space check — conservative: appdata × 1.1
-APPDATA_SIZE_KB=$(du -sk "$APPDATA_PATH" 2>/dev/null | cut -f1)
-OUTPUT_FREE_KB=$(df "$OUTPUT_DIR" --output=avail 2>/dev/null | tail -1 | tr -d ' ')
-REQUIRED_KB=$(( APPDATA_SIZE_KB * 11 / 10 ))
-APPDATA_SIZE_H=$(du -sh "$APPDATA_PATH" 2>/dev/null | cut -f1)
-OUTPUT_FREE_H=$(df -h "$OUTPUT_DIR" --output=avail 2>/dev/null | tail -1 | tr -d ' ')
+#
+# One traversal of the appdata tree, not two. This measured it twice — once with du -sk for the
+# arithmetic and again with du -sh for the message — and walked $OUTPUT_DIR twice as well. On a
+# container's appdata that is the expensive call in this script, paid twice to print a string.
+# An unreadable size is not a small size. Defaulting either of these to 0 makes the check below
+# pass — a zero requirement clears any free space, and the export then runs toward a disk that
+# was never measured. Unknown stops here instead.
+if ! APPDATA_SIZE_MB=$(dir_size_mb "$APPDATA_PATH"); then
+    error "Could not measure $APPDATA_PATH — refusing to export without a space check"
+    exit 1
+fi
+if ! OUTPUT_FREE_MB=$(disk_free_mb "$OUTPUT_DIR"); then
+    error "Could not read free space on $OUTPUT_DIR — refusing to export without a space check"
+    exit 1
+fi
+REQUIRED_MB=$(( APPDATA_SIZE_MB * 11 / 10 ))
+APPDATA_SIZE_H=$(format_mb "$APPDATA_SIZE_MB")
+OUTPUT_FREE_H=$(format_mb "$OUTPUT_FREE_MB")
 
-if [[ "$OUTPUT_FREE_KB" -lt "$REQUIRED_KB" ]]; then
+if [[ "$OUTPUT_FREE_MB" -lt "$REQUIRED_MB" ]]; then
     error "Insufficient space in $OUTPUT_DIR"
     error "Estimated need: ~${APPDATA_SIZE_H} (×1.1 conservative) — available: ${OUTPUT_FREE_H}"
     exit 1