diff --git a/web/skins/classic/views/js/zone.js b/web/skins/classic/views/js/zone.js
index 81e66814f..3f6e9cfb2 100644
--- a/web/skins/classic/views/js/zone.js
+++ b/web/skins/classic/views/js/zone.js
@@ -247,7 +247,7 @@ function applyZoneUnits()
     }
     else
     {
-        form.elements['newZone[TempArea]'].value = 100;
+        form.elements['newZone[TempArea]'].value = Math.round( area/monitorArea * 100 );
         toPercent( form.elements['newZone[MinAlarmPixels]'], area );
         toPercent( form.elements['newZone[MaxAlarmPixels]'], area );
         toPercent( form.elements['newZone[MinFilterPixels]'], area );
@@ -323,6 +323,7 @@ function updateZoneImage()
         Point.y = zone['Points'][i].y;
         Poly.points.appendItem( Point );
     }
+    updateArea();
 }
 
 function fixActivePoint( index )
@@ -356,6 +357,7 @@ function updateActivePoint( index )
     var Point =  $('zonePoly').points.getItem(index);
     Point.x =x;
     Point.y =y;
+  updateArea();
 
 }
 
@@ -379,6 +381,7 @@ function delPoint( index )
 {
     zone['Points'].splice( index, 1 );
     drawZonePoints();
+  updateArea();
 }
 
 function limitPointValue( point, loVal, hiVal )
@@ -386,6 +389,21 @@ function limitPointValue( point, loVal, hiVal )
     point.value = constrainValue(point.value, loVal, hiVal)
 }
 
+function updateArea( ) {
+  area = Polygon_calcArea( zone['Points'] );
+  zone.Area = area;
+  var form = $('zoneForm');
+  form.elements['newZone[Area]'].value = area;
+  if ( form.elements['newZone[Units]'].value == 'Percent' ) {
+
+    form.elements['newZone[TempArea]'].value = Math.round( area/monitorArea*100 );
+  } else if ( form.elements['newZone[Units]'].value == 'Pixels' ) {
+    form.elements['newZone[TempArea]'].value = area;
+  } else {
+    alert("Unknown units: " + form.elements['newZone[Units]'].value );
+  }
+}
+
 function updateX( index )
 {
     limitPointValue( $('newZone[Points]['+index+'][x]'), 0, maxX );
@@ -398,6 +416,7 @@ function updateX( index )
     var Point =  $('zonePoly').points.getItem(index);
     Point.x =x;
     Point.y =y;
+  updateArea();
 }
 
 function updateY( index )
@@ -412,6 +431,7 @@ function updateY( index )
     var Point =  $('zonePoly').points.getItem(index);
     Point.x =x;
     Point.y =y;
+  updateArea();
 }
 
 function saveChanges( element )
@@ -739,4 +759,16 @@ function initPage() {
         appletRefresh.delay( appletRefreshTime*1000 );
 }
 
+function Polygon_calcArea( coords ) {
+  var n_coords = coords.length;
+  var float_area = 0.0;
+
+  for ( i = 0, j = n_coords-1; i < n_coords; j = i++ ) {
+    var trap_area = ( ( coords[i].x - coords[j].x ) * ( coords[i].y + coords[j].y ) ) / 2;
+    float_area += trap_area;
+    //printf( "%.2f (%.2f)\n", float_area, trap_area );
+  }
+  return Math.round( Math.abs( float_area ) );
+}
+
 window.addEvent( 'domready', initPage );
diff --git a/web/skins/classic/views/js/zone.js.php b/web/skins/classic/views/js/zone.js.php
index 85f606d2a..e7f368085 100644
--- a/web/skins/classic/views/js/zone.js.php
+++ b/web/skins/classic/views/js/zone.js.php
@@ -48,6 +48,7 @@ zone['Points'][<?php echo $i ?>] = { 'x': <?php echo $newZone['Points'][$i]['x']
 
 var maxX = <?php echo $monitor->Width()-1 ?>;
 var maxY = <?php echo $monitor->Height()-1 ?>;
+var monitorArea = <?php echo $monitor->Width() * $monitor->Height() ?>;
 var selfIntersecting = <?php echo $selfIntersecting?'true':'false' ?>;
 
 var selfIntersectingString = '<?php echo addslashes(translate('SelfIntersecting')) ?>';