Setting HTML element width using ng-style and percentage value in AngularJS

The code within your ng-style attribute is a javascript object, so you could append a percentage symbol on the end of you width value. As you are appending a string to a number it will also convert the value of width to a string.

<div id="progressBackground" ... >
    <div id="progressBar"
         ng-model="..."
         ng-style="{ 'width': completionPercent + '%' }"
         ... ></div>
</div>