JSFiddle - React, Tailwind, and code Playground

HTML

<div class="square">
  <div class="dot calc"></div>
</div>

<div class="square">
  <div class="dot calc-x-y"></div>
</div>

<div class="square">
  <div class="dot transform"></div>
</div>

<div class="square">
  <div class="dot transform-x-y"></div>
</div>

CSS

.square{
  width: 100px;
  height: 100px;
  border: 1px solid;
  margin-bottom: 10px;
  position: relative;
}

.dot{
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: red;
}

.calc{
  position: absolute;
  left: calc(50% - 10px);
}

.transform{
  position: absolute;
  left: 50%;
  transform: translateX(-50%);
}

.calc-x-y{
  position: absolute;
  left: calc(50% - 10px);
  top: calc(50% - 10px);
}

.transform-x-y{
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
}