diff --git a/clusterize.js b/clusterize.js
index 6d331ba..de267e9 100644
--- a/clusterize.js
+++ b/clusterize.js
@@ -190,12 +190,18 @@
       opts.block_height = opts.item_height * opts.rows_in_block;
       opts.rows_in_cluster = opts.blocks_in_cluster * opts.rows_in_block;
       opts.cluster_height = opts.blocks_in_cluster * opts.block_height;
+      opts.top_offset = this.content_elem.offsetTop;
+      opts.content_height = (rows.length * opts.item_height);
       return prev_item_height != opts.item_height;
     },
     // get current cluster number
     getClusterNum: function () {
-      this.options.scroll_top = this.scroll_elem.scrollTop;
-      return Math.floor(this.options.scroll_top / (this.options.cluster_height - this.options.block_height)) || 0;
+      var opts = this.options;
+      opts.scroll_top = this.scroll_elem.scrollTop - opts.top_offset;
+      if (opts.scroll_top >= opts.content_height) {
+        return Math.floor(opts.scroll_top / opts.content_height);
+      }
+      return Math.floor(opts.scroll_top / (opts.cluster_height - opts.block_height));
     },
     // generate empty row if no data provided
     generateEmptyRow: function() {
diff --git a/clusterize.min.js b/clusterize.min.js
index b2d3c8e..b1a06c3 100644
--- a/clusterize.min.js
+++ b/clusterize.min.js
@@ -1,16 +1,17 @@
-/*! Clusterize.js - v0.17.6 - 2017-03-05
-* http://NeXTs.github.com/Clusterize.js/
-* Copyright (c) 2015 Denis Lukov; Licensed GPLv3 */
-
-;(function(q,n){"undefined"!=typeof module?module.exports=n():"function"==typeof define&&"object"==typeof define.amd?define(n):this[q]=n()})("Clusterize",function(){function q(b,a,c){return a.addEventListener?a.addEventListener(b,c,!1):a.attachEvent("on"+b,c)}function n(b,a,c){return a.removeEventListener?a.removeEventListener(b,c,!1):a.detachEvent("on"+b,c)}function r(b){return"[object Array]"===Object.prototype.toString.call(b)}function m(b,a){return window.getComputedStyle?window.getComputedStyle(a)[b]:
+/*
+ Clusterize.js - v0.17.6 - 2017-03-05
+ http://NeXTs.github.com/Clusterize.js/
+ Copyright (c) 2015 Denis Lukov; Licensed GPLv3 */
+(function(q,n){"undefined"!=typeof module?module.exports=n():"function"==typeof define&&"object"==typeof define.amd?define(n):this[q]=n()})("Clusterize",function(){function q(b,a,c){return a.addEventListener?a.addEventListener(b,c,!1):a.attachEvent("on"+b,c)}function n(b,a,c){return a.removeEventListener?a.removeEventListener(b,c,!1):a.detachEvent("on"+b,c)}function r(b){return"[object Array]"===Object.prototype.toString.call(b)}function m(b,a){return window.getComputedStyle?window.getComputedStyle(a)[b]:
 a.currentStyle[b]}var l=function(){for(var b=3,a=document.createElement("b"),c=a.all||[];a.innerHTML="\x3c!--[if gt IE "+ ++b+"]><i><![endif]--\x3e",c[0];);return 4<b?b:document.documentMode}(),x=navigator.platform.toLowerCase().indexOf("mac")+1,p=function(b){if(!(this instanceof p))return new p(b);var a=this,c={rows_in_block:50,blocks_in_cluster:4,tag:null,show_no_data_row:!0,no_data_class:"clusterize-no-data",no_data_text:"No data",keep_parity:!0,callbacks:{}};a.options={};for(var d="rows_in_block blocks_in_cluster show_no_data_row no_data_class no_data_text keep_parity tag callbacks".split(" "),
-f=0,h;h=d[f];f++)a.options[h]="undefined"!=typeof b[h]&&null!=b[h]?b[h]:c[h];c=["scroll","content"];for(f=0;d=c[f];f++)if(a[d+"_elem"]=b[d+"Id"]?document.getElementById(b[d+"Id"]):b[d+"Elem"],!a[d+"_elem"])throw Error("Error! Could not find "+d+" element");a.content_elem.hasAttribute("tabindex")||a.content_elem.setAttribute("tabindex",0);var e=r(b.rows)?b.rows:a.fetchMarkup(),g={};b=a.scroll_elem.scrollTop;a.insertToDOM(e,g);a.scroll_elem.scrollTop=b;var k=!1,m=0,l=!1,t=function(){x&&(l||(a.content_elem.style.pointerEvents=
-"none"),l=!0,clearTimeout(m),m=setTimeout(function(){a.content_elem.style.pointerEvents="auto";l=!1},50));k!=(k=a.getClusterNum())&&a.insertToDOM(e,g);a.options.callbacks.scrollingProgress&&a.options.callbacks.scrollingProgress(a.getScrollProgress())},u=0,v=function(){clearTimeout(u);u=setTimeout(a.refresh,100)};q("scroll",a.scroll_elem,t);q("resize",window,v);a.destroy=function(b){n("scroll",a.scroll_elem,t);n("resize",window,v);a.html((b?a.generateEmptyRow():e).join(""))};a.refresh=function(b){(a.getRowsHeight(e)||
-b)&&a.update(e)};a.update=function(b){e=r(b)?b:[];b=a.scroll_elem.scrollTop;e.length*a.options.item_height<b&&(k=a.scroll_elem.scrollTop=0);a.insertToDOM(e,g);a.scroll_elem.scrollTop=b};a.clear=function(){a.update([])};a.getRowsAmount=function(){return e.length};a.getScrollProgress=function(){return this.options.scroll_top/(e.length*this.options.item_height)*100||0};var w=function(b,c){var d=r(c)?c:[];d.length&&(e="append"==b?e.concat(d):d.concat(e),a.insertToDOM(e,g))};a.append=function(a){w("append",
+e=0,h;h=d[e];e++)a.options[h]="undefined"!=typeof b[h]&&null!=b[h]?b[h]:c[h];c=["scroll","content"];for(e=0;d=c[e];e++)if(a[d+"_elem"]=b[d+"Id"]?document.getElementById(b[d+"Id"]):b[d+"Elem"],!a[d+"_elem"])throw Error("Error! Could not find "+d+" element");a.content_elem.hasAttribute("tabindex")||a.content_elem.setAttribute("tabindex",0);var f=r(b.rows)?b.rows:a.fetchMarkup(),g={};b=a.scroll_elem.scrollTop;a.insertToDOM(f,g);a.scroll_elem.scrollTop=b;var k=!1,m=0,l=!1,t=function(){x&&(l||(a.content_elem.style.pointerEvents=
+"none"),l=!0,clearTimeout(m),m=setTimeout(function(){a.content_elem.style.pointerEvents="auto";l=!1},50));k!=(k=a.getClusterNum())&&a.insertToDOM(f,g);a.options.callbacks.scrollingProgress&&a.options.callbacks.scrollingProgress(a.getScrollProgress())},u=0,v=function(){clearTimeout(u);u=setTimeout(a.refresh,100)};q("scroll",a.scroll_elem,t);q("resize",window,v);a.destroy=function(b){n("scroll",a.scroll_elem,t);n("resize",window,v);a.html((b?a.generateEmptyRow():f).join(""))};a.refresh=function(b){(a.getRowsHeight(f)||
+b)&&a.update(f)};a.update=function(b){f=r(b)?b:[];b=a.scroll_elem.scrollTop;f.length*a.options.item_height<b&&(k=a.scroll_elem.scrollTop=0);a.insertToDOM(f,g);a.scroll_elem.scrollTop=b};a.clear=function(){a.update([])};a.getRowsAmount=function(){return f.length};a.getScrollProgress=function(){return this.options.scroll_top/(f.length*this.options.item_height)*100||0};var w=function(b,c){var d=r(c)?c:[];d.length&&(f="append"==b?f.concat(d):d.concat(f),a.insertToDOM(f,g))};a.append=function(a){w("append",
 a)};a.prepend=function(a){w("prepend",a)}};p.prototype={constructor:p,fetchMarkup:function(){for(var b=[],a=this.getChildNodes(this.content_elem);a.length;)b.push(a.shift().outerHTML);return b},exploreEnvironment:function(b,a){var c=this.options;c.content_tag=this.content_elem.tagName.toLowerCase();b.length&&(l&&9>=l&&!c.tag&&(c.tag=b[0].match(/<([^>\s/]*)/)[1].toLowerCase()),1>=this.content_elem.children.length&&(a.data=this.html(b[0]+b[0]+b[0])),c.tag||(c.tag=this.content_elem.children[0].tagName.toLowerCase()),
-this.getRowsHeight(b))},getRowsHeight:function(b){var a=this.options,c=a.item_height;a.cluster_height=0;if(b.length){b=this.content_elem.children;var d=b[Math.floor(b.length/2)];a.item_height=d.offsetHeight;"tr"==a.tag&&"collapse"!=m("borderCollapse",this.content_elem)&&(a.item_height+=parseInt(m("borderSpacing",this.content_elem),10)||0);"tr"!=a.tag&&(b=parseInt(m("marginTop",d),10)||0,d=parseInt(m("marginBottom",d),10)||0,a.item_height+=Math.max(b,d));a.block_height=a.item_height*a.rows_in_block;
-a.rows_in_cluster=a.blocks_in_cluster*a.rows_in_block;a.cluster_height=a.blocks_in_cluster*a.block_height;return c!=a.item_height}},getClusterNum:function(){this.options.scroll_top=this.scroll_elem.scrollTop;return Math.floor(this.options.scroll_top/(this.options.cluster_height-this.options.block_height))||0},generateEmptyRow:function(){var b=this.options;if(!b.tag||!b.show_no_data_row)return[];var a=document.createElement(b.tag),c=document.createTextNode(b.no_data_text),d;a.className=b.no_data_class;
-"tr"==b.tag&&(d=document.createElement("td"),d.colSpan=100,d.appendChild(c));a.appendChild(d||c);return[a.outerHTML]},generate:function(b,a){var c=this.options,d=b.length;if(d<c.rows_in_block)return{top_offset:0,bottom_offset:0,rows_above:0,rows:d?b:this.generateEmptyRow()};var f=Math.max((c.rows_in_cluster-c.rows_in_block)*a,0),h=f+c.rows_in_cluster,e=Math.max(f*c.item_height,0),c=Math.max((d-h)*c.item_height,0),d=[],g=f;for(1>e&&g++;f<h;f++)b[f]&&d.push(b[f]);return{top_offset:e,bottom_offset:c,
-rows_above:g,rows:d}},renderExtraTag:function(b,a){var c=document.createElement(this.options.tag);c.className=["clusterize-extra-row","clusterize-"+b].join(" ");a&&(c.style.height=a+"px");return c.outerHTML},insertToDOM:function(b,a){this.options.cluster_height||this.exploreEnvironment(b,a);var c=this.generate(b,this.getClusterNum()),d=c.rows.join(""),f=this.checkChanges("data",d,a),h=this.checkChanges("top",c.top_offset,a),e=this.checkChanges("bottom",c.bottom_offset,a),g=this.options.callbacks,
-k=[];f||h?(c.top_offset&&(this.options.keep_parity&&k.push(this.renderExtraTag("keep-parity")),k.push(this.renderExtraTag("top-space",c.top_offset))),k.push(d),c.bottom_offset&&k.push(this.renderExtraTag("bottom-space",c.bottom_offset)),g.clusterWillChange&&g.clusterWillChange(),this.html(k.join("")),"ol"==this.options.content_tag&&this.content_elem.setAttribute("start",c.rows_above),g.clusterChanged&&g.clusterChanged()):e&&(this.content_elem.lastChild.style.height=c.bottom_offset+"px")},html:function(b){var a=
-this.content_elem;if(l&&9>=l&&"tr"==this.options.tag){var c=document.createElement("div");for(c.innerHTML="<table><tbody>"+b+"</tbody></table>";b=a.lastChild;)a.removeChild(b);for(c=this.getChildNodes(c.firstChild.firstChild);c.length;)a.appendChild(c.shift())}else a.innerHTML=b},getChildNodes:function(b){b=b.children;for(var a=[],c=0,d=b.length;c<d;c++)a.push(b[c]);return a},checkChanges:function(b,a,c){var d=a!=c[b];c[b]=a;return d}};return p});
\ No newline at end of file
+this.getRowsHeight(b))},getRowsHeight:function(b){var a=this.options,c=a.item_height;a.cluster_height=0;if(b.length){var d=this.content_elem.children,e=d[Math.floor(d.length/2)];a.item_height=e.offsetHeight;"tr"==a.tag&&"collapse"!=m("borderCollapse",this.content_elem)&&(a.item_height+=parseInt(m("borderSpacing",this.content_elem),10)||0);"tr"!=a.tag&&(d=parseInt(m("marginTop",e),10)||0,e=parseInt(m("marginBottom",e),10)||0,a.item_height+=Math.max(d,e));a.block_height=a.item_height*a.rows_in_block;
+a.rows_in_cluster=a.blocks_in_cluster*a.rows_in_block;a.cluster_height=a.blocks_in_cluster*a.block_height;a.top_offset=this.content_elem.offsetTop;a.content_height=b.length*a.item_height;return c!=a.item_height}},getClusterNum:function(){var b=this.options;b.scroll_top=this.scroll_elem.scrollTop-b.top_offset;return b.scroll_top>=b.content_height?Math.floor(b.scroll_top/b.content_height):Math.floor(b.scroll_top/(b.cluster_height-b.block_height))},generateEmptyRow:function(){var b=this.options;if(!b.tag||
+!b.show_no_data_row)return[];var a=document.createElement(b.tag),c=document.createTextNode(b.no_data_text),d;a.className=b.no_data_class;"tr"==b.tag&&(d=document.createElement("td"),d.colSpan=100,d.appendChild(c));a.appendChild(d||c);return[a.outerHTML]},generate:function(b,a){var c=this.options,d=b.length;if(d<c.rows_in_block)return{top_offset:0,bottom_offset:0,rows_above:0,rows:d?b:this.generateEmptyRow()};var e=Math.max((c.rows_in_cluster-c.rows_in_block)*a,0),h=e+c.rows_in_cluster,f=Math.max(e*
+c.item_height,0),c=Math.max((d-h)*c.item_height,0),d=[],g=e;for(1>f&&g++;e<h;e++)b[e]&&d.push(b[e]);return{top_offset:f,bottom_offset:c,rows_above:g,rows:d}},renderExtraTag:function(b,a){var c=document.createElement(this.options.tag);c.className=["clusterize-extra-row","clusterize-"+b].join(" ");a&&(c.style.height=a+"px");return c.outerHTML},insertToDOM:function(b,a){this.options.cluster_height||this.exploreEnvironment(b,a);var c=this.generate(b,this.getClusterNum()),d=c.rows.join(""),e=this.checkChanges("data",
+d,a),h=this.checkChanges("top",c.top_offset,a),f=this.checkChanges("bottom",c.bottom_offset,a),g=this.options.callbacks,k=[];e||h?(c.top_offset&&(this.options.keep_parity&&k.push(this.renderExtraTag("keep-parity")),k.push(this.renderExtraTag("top-space",c.top_offset))),k.push(d),c.bottom_offset&&k.push(this.renderExtraTag("bottom-space",c.bottom_offset)),g.clusterWillChange&&g.clusterWillChange(),this.html(k.join("")),"ol"==this.options.content_tag&&this.content_elem.setAttribute("start",c.rows_above),
+g.clusterChanged&&g.clusterChanged()):f&&(this.content_elem.lastChild.style.height=c.bottom_offset+"px")},html:function(b){var a=this.content_elem;if(l&&9>=l&&"tr"==this.options.tag){var c=document.createElement("div");for(c.innerHTML="<table><tbody>"+b+"</tbody></table>";b=a.lastChild;)a.removeChild(b);for(c=this.getChildNodes(c.firstChild.firstChild);c.length;)a.appendChild(c.shift())}else a.innerHTML=b},getChildNodes:function(b){b=b.children;for(var a=[],c=0,d=b.length;c<d;c++)a.push(b[c]);return a},
+checkChanges:function(b,a,c){var d=a!=c[b];c[b]=a;return d}};return p});