diff --git a/status/CHANGELOG b/status/CHANGELOG
index 2bd3c9400..6cce3d3f3 100644
--- a/status/CHANGELOG
+++ b/status/CHANGELOG
@@ -67,3 +67,5 @@ Added an option to the SSH monitor type for a port number.
 ---- Changes since 1.490 ----
 Added a new monitor type for detecting large directories.
 Added a button to the main page for refreshing only selected monitors, thanks to Michael Mansour.
+---- Changes since 1.500 ----
+Added an option to the Disk Space monitor to alert based on percentage free, as an alternative to a threshold in bytes.
diff --git a/status/lang/en b/status/lang/en
index 33cbc8cf5..7da171759 100644
--- a/status/lang/en
+++ b/status/lang/en
@@ -237,13 +237,18 @@ traffic_ebytes=Missing or invalid number of bytes/second
 
 space_fs=Filesystem to check
 space_min2=Minimum free space
+space_mode0=Absolute size
+space_mode1=Percentage of total
 space_desc=$1 free
 space_nofs=Filesystem not mounted
 space_other=Other..
 space_emin=Missing or invalid free space
+space_epc=Missing or invalid free space percentage
 space_eother=Missing or invalid filesystem
 space_inode=Minimum free Inodes
 space_ierr=Only $1 inodes free
+space_merr=Only $1 space free
+space_perr=Only $1% free
 
 load_time=Load average to check
 load_1=1 minute
diff --git a/status/space-monitor.pl b/status/space-monitor.pl
index 5c39d0739..acff6040b 100755
--- a/status/space-monitor.pl
+++ b/status/space-monitor.pl
@@ -11,8 +11,21 @@ foreach $f (&mount::list_mounted()) {
 	}
 if ($m) {
 	local @sp = &mount::disk_space($m->[2], $m->[0]);
-	if ($sp[1] < $_[0]->{'min'}) {
-		return { 'up' => 0 };
+	if ($_[0]->{'min'} =~ /^(\S+)%/) {
+		# Compare percentage
+		local $pc = $sp[1] * 100.0 / $sp[0];
+		if ($pc < $1) {
+			return { 'up' => 0,
+				 'desc' => &text('space_perr', int($pc)) };
+			}
+		}
+	else {
+		# Compare absolute size
+		if ($sp[1] < $_[0]->{'min'}) {
+			return { 'up' => 0,
+				 'desc' => &text('space_merr',
+						 &nice_size($sp[1]*1024)) };
+			}
 		}
 
 	if ($_[0]->{'inode'} && defined(&mount::inode_space)) {
@@ -54,9 +67,17 @@ else {
 		&ui_textbox("other", $_[0]->{'fs'}, 30));
 	}
 
+# Minumum free space
+local $min = $_[0]->{'min'};
+local $pc = ($min =~ s/\%$// ? 1 : 0);
 print &ui_table_row($text{'space_min2'},
-	&ui_bytesbox("min", $_[0]->{'min'}*1024));
+	&ui_radio_table("min_mode", $pc,
+		[ [ 0, $text{'space_mode0'},
+		    &ui_bytesbox("min", $pc ? undef : $min*1024) ],
+		  [ 1, $text{'space_mode1'},
+		    &ui_textbox("pc", $pc ? $min : undef, 4)."%" ] ]), 3);
 
+# Minimum free inodes
 if (defined(&mount::inode_space)) {
 	print &ui_table_row($text{'space_inode'},
 		&ui_textbox("inode", $_[0]->{'inode'}, 10));
@@ -66,8 +87,15 @@ if (defined(&mount::inode_space)) {
 sub parse_space_dialog
 {
 &depends_check($_[0], "mount");
-$in{'min'} =~ /^[0-9\.]+$/ || &error($text{'space_emin'});
-$_[0]->{'min'} = $in{'min'}*$in{'min_units'}/1024;
+if ($in{'min_mode'} == 0) {
+	$in{'min'} =~ /^[0-9\.]+$/ || &error($text{'space_emin'});
+	$_[0]->{'min'} = $in{'min'}*$in{'min_units'}/1024;
+	}
+else {
+	$in{'pc'} =~ /^[0-9\.]+$/ && $in{'pc'} >= 0 && $in{'pc'} <= 100 ||
+		&error($text{'space_epc'});
+	$_[0]->{'min'} = $in{'pc'}."%";
+	}
 if ($in{'fs'}) {
 	$_[0]->{'fs'} = $in{'fs'};
 	}