<!DOCTYPE html>

<style>
  .item { height: 50px; width: 50px; border: 1px solid blue; }

  .container { height: 100px; border: 5px solid pink; }
  table { border: 2px solid red; border-collapse: collapse; }
  td { border: 2px solid green; }
</style>

<table>
  <td>
    <div class="item"></div>
  </td>
</table>

<table>
  <td>
    <div class="item"></div>
  </td>
</table>

<div class="container">
  <table style="height: 100%; box-sizing: border-box;">
    <td>
      <div class="item"></div>
    </td>
  </table>
</div>


<table class="container">
  <td style="height: 79px;">
    <div class="item"></div>
  </td>
</table>