diff --git a/doc/ChangeLog b/doc/ChangeLog
index 225db2937..33adac5dc 100644
--- a/doc/ChangeLog
+++ b/doc/ChangeLog
@@ -1,3 +1,8 @@
+2008-11-10  Carsten Dominik  <carsten.dominik@gmail.com>
+
+	* org.texi (Clocking work time): Document the :formula property of
+	clock tables.
+
 2008-11-09  Carsten Dominik  <carsten.dominik@gmail.com>
 
 	* org.texi (Agenda commands): Document the double-prefix version
diff --git a/doc/org.texi b/doc/org.texi
index 04f14a2f8..f13d3efe8 100644
--- a/doc/org.texi
+++ b/doc/org.texi
@@ -4830,6 +4830,10 @@ new table.  The @samp{BEGIN} line can specify options:
 :step        @r{@code{week} or @code{day}, to split the table into chunks.}
              @r{To use this, @code{:block} or @code{:tstart}, @code{:tend} are needed.}
 :link        @r{Link the item headlines in the table to their origins}
+:formula     @r{Content of a @code{#+TBLFM} line to be added and evaluated.}
+             @r{As a special case, @samp{:formula %} adds column with % time.}
+             @r{If you do not specify a formula here, any existing formula}
+             @r{below the clock table will survive updates and be evaluated.}
 @end example
 So to get a clock summary of the current level 1 tree, for the current
 day, you could write
@@ -4845,6 +4849,11 @@ only to fit it onto the manual.}
                     :tend "<2006-08-10 Thu 12:00>"
 #+END: clocktable
 @end example
+A summary of the current subtree with % times would be
+@example
+#+BEGIN: clocktable :scope subtree :link t :formula %
+#+END: clocktable
+@end example
 @kindex C-c C-c
 @item C-c C-c
 @kindex C-c C-x C-u
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 0819e08dd..84c685b18 100755
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,7 @@
 2008-11-10  Carsten Dominik  <carsten.dominik@gmail.com>
 
+	* org-clock.el (org-clock-time%): New function.
+
 	* org.el (org-entry-get, org-entry-delete): Use safer regexps to
 	retrieve property values.
 
diff --git a/lisp/org-clock.el b/lisp/org-clock.el
index 4b59db3cb..ec566d500 100644
--- a/lisp/org-clock.el
+++ b/lisp/org-clock.el
@@ -819,7 +819,7 @@ the currently selected interval size."
 	   (te (plist-get params :tend))
 	   (block (plist-get params :block))
 	   (link (plist-get params :link))
-	   ipos time p level hlc hdl
+	   ipos time p level hlc hdl content recalc formula pcol
 	   cc beg end pos tbl tbl1 range-text rm-file-column scope-is-list)
       (setq org-clock-file-total-minutes nil)
       (when step
@@ -959,9 +959,37 @@ the currently selected interval size."
 				  'identity (delq nil tbl)
 				  (if scope-is-list "\n|-\n" "\n")))
 	  (backward-delete-char 1)
+	  (if (setq formula (plist-get params :formula))
+	      (cond
+	       ((eq formula '%)
+		(setq pcol (+ (if scope-is-list 1 0) maxlevel 3))
+		(insert 
+		 (format 
+		  "\n#+TBLFM: $%d='(org-clock-time%% @%d$%d $%d..$%d);%%.1f"
+		  pcol
+		  2
+		  (+ 3 (if scope-is-list 1 0))
+		  (+ (if scope-is-list 1 0) 3)
+		  (1- pcol)))
+		(setq recalc t))
+	       ((stringp formula)
+		(insert "\n#+TBLFM: " formula)
+		(setq recalc t))
+	       (t (error "invalid formula in clocktable")))
+	    ;; Should we rescue an old formula?
+	    (when (stringp (setq content (plist-get params :content)))
+	      (when (string-match "^\\(#\\+TBLFM:.*\\)" content)
+		(setq recalc t)
+		(insert "\n" (match-string 1 (plist-get params :content)))
+		(beginning-of-line 0))))
 	  (goto-char ipos)
 	  (skip-chars-forward "^|")
 	  (org-table-align)
+	  (when recalc
+	    (if (eq formula '%)
+		(save-excursion (org-table-goto-column pcol nil 'force)
+				(insert "%")))
+	    (org-table-recalculate 'all))
 	  (when rm-file-column
 	    (forward-char 1)
 	    (org-table-delete-column)))))))
@@ -1010,6 +1038,29 @@ the currently selected interval size."
 			   lines)
 		   "\n"))))
 
+(defun org-clock-time% (total &rest strings)
+  "Compute a time fraction in percent.
+TOTAL s a time string like 10:21 specifying the total times.
+STRINGS is a list of strings that should be checked for a time.
+The first string that does have a time will be used.
+This function is made for clock tables."
+  (let ((re "\\([0-9]+\\):\\([0-9]+\\)")
+	tot s)
+    (save-match-data
+      (catch 'exit
+	(if (not (string-match re total))
+	    (throw 'exit 0.)
+	  (setq tot (+ (string-to-number (match-string 2 total))
+		       (* 60 (string-to-number (match-string 1 total)))))
+	  (if (= tot 0.) (throw 'exit 0.)))
+	(while (setq s (pop strings))
+	  (if (string-match "\\([0-9]+\\):\\([0-9]+\\)" s)
+	      (throw 'exit
+		     (/ (* 100.0 (+ (string-to-number (match-string 2 s))
+				    (* 60 (string-to-number (match-string 1 s)))))
+			tot))))
+	0))))
+
 (defun org-clock-save ()
   "Persist various clock-related data to disk"
   (with-current-buffer (find-file (expand-file-name org-clock-persist-file))