Element: clientTop property

The width of the top border of an element in pixels. It is a read-only, integer property of element.

As it happens, all that lies between the two locations (offsetTop and client area top) is the element's border. This is because the offsetTop indicates the location of the top of the border (not the margin) while the client area starts immediately below the border, (client area includes padding.) Therefore, the clientTop value will always equal the integer portion of the .getComputedStyle() value for "border-top-width". (Actually might be Math.round(parseFloat()).) For example, if the computed "border-top-width" is zero, then clientTop is also zero.

<div id="container">
  <div id="contained">
    <p>
      Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
      tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim
      veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea
      commodo consequat.
    </p>
  </div>
</div>

#container {
  margin: 3rem;
  background-color: rgb(255 255 204);
  border: 4px dashed black;
}

#contained {
  margin: 1rem;
  border-top: 24px black solid;
  padding: 0px 28px;
  overflow: auto;
  background-color: white;
}