Using calc()

• The calc() function is the part of a new syntax in CSS3 in which you can calculate (mathematically) what size/position
  your element occupies by using a variety of values like pixels, percentages, etc.

• Note: Whenever you use this function, always take care of the space between two values calc(100% - 80px)

   <div class="center"></div>

 .center {
    position: absolute;
    height: 50px;
    width: 50px;
    background: red;
    top: calc(50% - 50px / 2); /* height divided by 2*/
    left: calc(50% - 50px / 2); /* width divided by 2*/
 }