diff --git a/guile/sort-buckets.scm b/guile/sort-buckets.scm
new file mode 100644
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+++ b/guile/sort-buckets.scm
@@ -0,0 +1,48 @@
+#!/usr/bin/guile \
+--no-auto-compile -e main -s
+
+Sort Buckets: script to sort a CSV of bucket-name,size in descending order of
+bucket size.
+
+Copyright (C) 2025 Ray Miller <ray@1729.org.uk>.
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+!#
+
+(use-modules (ice-9 match)
+             (srfi srfi-1)
+             (dsv))
+
+(define (parse-size s)
+  (match-let (((val unit) (string-split s #\space)))
+    (let ((val (string->number val)))
+      (match unit
+        ("Bytes" val)
+        ("KiB" (* 1024 val))
+        ("MiB" (* 1024 1024 val))
+        ("GiB" (* 1024 1024 1024 val))
+        ("TiB" (* 1024 1024 1024 1024 val))))))
+
+(define (sort-csv in-file out-file)
+  (let* ((data (call-with-input-file in-file (lambda (port) (dsv->scm port #:format 'rfc4180))))
+         (sorted (map cdr (sort-list
+                           (map (lambda (xs) (cons (parse-size (last xs)) xs)) data)
+                           (lambda (a b) (> (first a) (first b)))))))
+    (call-with-output-file out-file (lambda (port) (scm->dsv port #:format 'rfc4180)))))
+
+(define (main args)
+  (case (length args)
+    ((3) (sort-csv (second args) (third args)))
+    ((2) (sort-csv (second args) (second args)))
+    (else (error "Usage: sort-buckets FILENAME [OUTPUT]"))))