diff --git a/README.md b/README.md
index 56538f1..729fb9c 100644
--- a/README.md
+++ b/README.md
@@ -415,10 +415,12 @@ The base element.
 - __padding__ - amount of padding on the inside of the element. can be a number
   or an object containing the properties: `left`, `right`, `top`, and `bottom`.
 - __width, height__ - width/height of the element, can be a number, percentage
-  (`0-100%`), or keyword (`half` or `shrink`).
+  (`0-100%`), or keyword (`half` or `shrink`). percentages can also have
+  offsets (`50%+1`, `50%-1`).
 - __left, right, top, bottom__ - offsets of the element __relative to its
   parent__. can be a number, percentage (`0-100%`), or keyword (`center`).
-  `right` and `bottom` do not accept keywords.
+  `right` and `bottom` do not accept keywords. percentages can also have
+  offsets (`50%+1`, `50%-1`).
 - __position__ - can contain the above options.
 - __scrollable__ - whether the element is scrollable or not.
 - __ch__ - background character (default is whitespace ` `).
@@ -1339,6 +1341,15 @@ var box = blessed.box({
 This tells blessed to create a box, perfectly centered __relative to its
 parent__, 50% as wide and 50% as tall as its parent.
 
+Percentages can also have offsets applied to them:
+
+``` js
+  ...
+  height: '50%-1',
+  left: '45%+1',
+  ...
+```
+
 To access the calculated offsets, relative to the parent:
 
 ``` js
diff --git a/lib/widget.js b/lib/widget.js
index 44968b1..2af6402 100644
--- a/lib/widget.js
+++ b/lib/widget.js
@@ -2934,12 +2934,17 @@ Element.prototype._getPos = function() {
 Element.prototype._getWidth = function(get) {
   var parent = get ? this.parent._getPos() : this.parent
     , width = this.position.width || 0
-    , left;
+    , left
+    , expr;
 
   if (typeof width === 'string') {
     if (width === 'half') width = '50%';
+    expr = width.split(/(?=\+|-)/);
+    width = expr[0];
     width = +width.slice(0, -1) / 100;
-    return parent.width * width | 0;
+    width = parent.width * width | 0;
+    width += +(expr[1] || 0);
+    return width;
   }
 
   // This is for if the element is being streched or shrunken.
@@ -2952,8 +2957,11 @@ Element.prototype._getWidth = function(get) {
     left = this.position.left || 0;
     if (typeof left === 'string') {
       if (left === 'center') left = '50%';
+      expr = left.split(/(?=\+|-)/);
+      left = expr[0];
       left = +left.slice(0, -1) / 100;
       left = parent.width * left | 0;
+      left += +(expr[1] || 0);
     }
     width = parent.width - (this.position.right || 0) - left;
     if (this.screen.autoPadding) {
@@ -2975,12 +2983,17 @@ Element.prototype.__defineGetter__('width', function() {
 Element.prototype._getHeight = function(get) {
   var parent = get ? this.parent._getPos() : this.parent
     , height = this.position.height || 0
-    , top;
+    , top
+    , expr;
 
   if (typeof height === 'string') {
     if (height === 'half') height = '50%';
+    expr = height.split(/(?=\+|-)/);
+    height = expr[0];
     height = +height.slice(0, -1) / 100;
-    return parent.height * height | 0;
+    height = parent.height * height | 0;
+    height += +(expr[1] || 0);
+    return height;
   }
 
   // This is for if the element is being streched or shrunken.
@@ -2993,8 +3006,11 @@ Element.prototype._getHeight = function(get) {
     top = this.position.top || 0;
     if (typeof top === 'string') {
       if (top === 'center') top = '50%';
+      expr = top.split(/(?=\+|-)/);
+      top = expr[0];
       top = +top.slice(0, -1) / 100;
       top = parent.height * top | 0;
+      top += +(expr[1] || 0);
     }
     height = parent.height - (this.position.bottom || 0) - top;
     if (this.screen.autoPadding) {
@@ -3016,12 +3032,16 @@ Element.prototype.__defineGetter__('height', function() {
 
 Element.prototype._getLeft = function(get) {
   var parent = get ? this.parent._getPos() : this.parent
-    , left = this.position.left || 0;
+    , left = this.position.left || 0
+    , expr;
 
   if (typeof left === 'string') {
     if (left === 'center') left = '50%';
+    expr = left.split(/(?=\+|-)/);
+    left = expr[0];
     left = +left.slice(0, -1) / 100;
     left = parent.width * left | 0;
+    left += +(expr[1] || 0);
     if (this.position.left === 'center') {
       left -= this._getWidth(get) / 2 | 0;
     }
@@ -3073,12 +3093,16 @@ Element.prototype.__defineGetter__('aright', function() {
 
 Element.prototype._getTop = function(get) {
   var parent = get ? this.parent._getPos() : this.parent
-    , top = this.position.top || 0;
+    , top = this.position.top || 0
+    , expr;
 
   if (typeof top === 'string') {
     if (top === 'center') top = '50%';
+    expr = top.split(/(?=\+|-)/);
+    top = expr[0];
     top = +top.slice(0, -1) / 100;
     top = parent.height * top | 0;
+    top += +(expr[1] || 0);
     if (this.position.top === 'center') {
       top -= this._getHeight(get) / 2 | 0;
     }
@@ -3155,6 +3179,7 @@ Element.prototype.__defineGetter__('rbottom', function() {
 // the parent was resized, etc.
 Element.prototype.__defineSetter__('width', function(val) {
   if (this.position.width === val) return;
+  if (/^\d+$/.test(val)) val = +val;
   this.emit('resize');
   this.clearPos();
   return this.position.width = val;
@@ -3162,19 +3187,24 @@ Element.prototype.__defineSetter__('width', function(val) {
 
 Element.prototype.__defineSetter__('height', function(val) {
   if (this.position.height === val) return;
+  if (/^\d+$/.test(val)) val = +val;
   this.emit('resize');
   this.clearPos();
   return this.position.height = val;
 });
 
 Element.prototype.__defineSetter__('aleft', function(val) {
+  var expr;
   if (typeof val === 'string') {
     if (val === 'center') {
       val = this.screen.width / 2 | 0;
       val -= this.width / 2 | 0;
     } else {
+      expr = val.split(/(?=\+|-)/);
+      val = expr[0];
       val = +val.slice(0, -1) / 100;
       val = this.screen.width * val | 0;
+      val += +(expr[1] || 0);
     }
   }
   val -= this.parent.aleft;
@@ -3193,13 +3223,17 @@ Element.prototype.__defineSetter__('aright', function(val) {
 });
 
 Element.prototype.__defineSetter__('atop', function(val) {
+  var expr;
   if (typeof val === 'string') {
     if (val === 'center') {
       val = this.screen.height / 2 | 0;
       val -= this.height / 2 | 0;
     } else {
+      expr = val.split(/(?=\+|-)/);
+      val = expr[0];
       val = +val.slice(0, -1) / 100;
       val = this.screen.height * val | 0;
+      val += +(expr[1] || 0);
     }
   }
   val -= this.parent.atop;
@@ -3219,6 +3253,7 @@ Element.prototype.__defineSetter__('abottom', function(val) {
 
 Element.prototype.__defineSetter__('rleft', function(val) {
   if (this.position.left === val) return;
+  if (/^\d+$/.test(val)) val = +val;
   this.emit('move');
   this.clearPos();
   return this.position.left = val;
@@ -3233,6 +3268,7 @@ Element.prototype.__defineSetter__('rright', function(val) {
 
 Element.prototype.__defineSetter__('rtop', function(val) {
   if (this.position.top === val) return;
+  if (/^\d+$/.test(val)) val = +val;
   this.emit('move');
   this.clearPos();
   return this.position.top = val;
@@ -3869,6 +3905,8 @@ Element.prototype.render = function() {
       if (!lines[y]) break;
       if (coords.noleft && x === xi) continue;
       if (coords.noright && x === xl - 1) continue;
+      cell = lines[y][x];
+      if (!cell) break;
       if (this.border.type === 'line') {
         if (x === xi) {
           ch = '┌';
@@ -3930,8 +3968,6 @@ Element.prototype.render = function() {
       } else if (this.border.type === 'bg') {
         ch = this.border.ch;
       }
-      cell = lines[y][x];
-      if (!cell) break;
       if (battr !== cell[0] || ch !== cell[1]) {
         lines[y][x][0] = battr;
         lines[y][x][1] = ch;
@@ -3941,6 +3977,8 @@ Element.prototype.render = function() {
     y = yi + 1;
     for (; y < yl - 1; y++) {
       if (!lines[y]) break;
+      cell = lines[y][xi];
+      if (!cell) break;
       if (this.border.type === 'line') {
         ch = '│';
         if (this.screen.dockBorders || this.dockBorders) {
@@ -3953,14 +3991,14 @@ Element.prototype.render = function() {
       } else if (this.border.type === 'bg') {
         ch = this.border.ch;
       }
-      cell = lines[y][xi];
-      if (!cell) break;
       if (!coords.noleft)
       if (battr !== cell[0] || ch !== cell[1]) {
         lines[y][xi][0] = battr;
         lines[y][xi][1] = ch;
         lines[y].dirty = true;
       }
+      cell = lines[y][xl - 1];
+      if (!cell) break;
       if (this.border.type === 'line') {
         ch = '│';
         if (this.screen.dockBorders || this.dockBorders) {
@@ -3986,8 +4024,6 @@ Element.prototype.render = function() {
       } else if (this.border.type === 'bg') {
         ch = this.border.ch;
       }
-      cell = lines[y][xl - 1];
-      if (!cell) break;
       if (!coords.noright)
       if (battr !== cell[0] || ch !== cell[1]) {
         lines[y][xl - 1][0] = battr;
@@ -4001,6 +4037,8 @@ Element.prototype.render = function() {
       if (!lines[y]) break;
       if (coords.noleft && x === xi) continue;
       if (coords.noright && x === xl - 1) continue;
+      cell = lines[y][x];
+      if (!cell) break;
       if (this.border.type === 'line') {
         if (x === xi) {
           ch = '└';
@@ -4064,8 +4102,6 @@ Element.prototype.render = function() {
       } else if (this.border.type === 'bg') {
         ch = this.border.ch;
       }
-      cell = lines[y][x];
-      if (!cell) break;
       if (battr !== cell[0] || ch !== cell[1]) {
         lines[y][x][0] = battr;
         lines[y][x][1] = ch;
diff --git a/test/widget-dock.js b/test/widget-dock.js
index 9a55404..4a47798 100644
--- a/test/widget-dock.js
+++ b/test/widget-dock.js
@@ -11,18 +11,18 @@ blessed.box({
   parent: screen,
   left: 0,
   top: 0,
-  width: 10,
-  height: 5,
+  width: '50%',
+  height: '50%',
   border: 'line',
   content: 'Foo'
 });
 
 blessed.box({
   parent: screen,
-  left: 9,
+  left: '50%-1',
   top: 0,
-  width: 10,
-  height: 5,
+  width: '50%+1',
+  height: '50%',
   content: 'Bar',
   border: 'line'
 });
@@ -30,19 +30,19 @@ blessed.box({
 blessed.box({
   parent: screen,
   left: 0,
-  top: 4,
-  width: 10,
-  height: 5,
+  top: '50%-1',
+  width: '50%',
+  height: '50%+1',
   border: 'line',
   content: 'Foo'
 });
 
 blessed.box({
   parent: screen,
-  left: 9,
-  top: 4,
-  width: 10,
-  height: 5,
+  left: '50%-1',
+  top: '50%-1',
+  width: '50%+1',
+  height: '50%+1',
   border: 'line',
   content: 'Bar'
 });