Mat-icon does not center in its div

You can use the flex Layout to align the icon

<div fxLayout="row" fxLayoutAlign="center">
  <mat-icon fxFlexAlign="center">supervisor_account</mat-icon>
</div>

Read more about flexLayout in the documentation, fxLayout row is the same as:

div {
  display:flex;
  flex-direction:row;
  justify-content:center; /* For fxLayoutAlign="center" */
}

Then you further align the flex item to center i.e fxFlexAlign="center"

mat-icon {
  display:flex;             
  align-self:center; 
}

What works for me is to use flex-container (justify-content / align-items to center) along with these properties font-size, widthand height - depending on your font size, which drives the other two properties:

::ng-deep .mat-icon {
  font-size: 48px;
  width: 48px;
  height: 48px;
}

You can add vertical align to the mat-icon element or .mat-icon class:

To override all material icons with global CSS: Stackblitz

.mat-icon {
    vertical-align: middle;
}

ATENTION: If your text have capital letters, add negative margin to prevent visual issues on some browsers (Stackblitz demo).
Also you can simply use vertical-align: sub or vertical-align: bottom if fits better with your requirements. Check following alignment MDN demo

---

Using FLEX with a container element for each icon/text: Stackblitz

CSS:

.icon-text {
    display: flex;
    align-items: center;
}

HTML:

<div class="icon-text">
   <mat-icon>home</mat-icon>
   <span>Some text here 1</span>
</div>

---

To style a particular material icon with utility class: Stackblitz

In some global css file:

.v-align-middle { 
    vertical-align: middle;
}

HTML:

<div>
   <mat-icon class="v-align-middle">home</mat-icon>
   <span class="v-align-middle">Some text here 1</span>
</div>

** some css frameworks already have classes like this, eg: bootstrap 4 **

---

To style a particular material icon: Stackblitz

CSS:

.custom-class mat-icon {
    vertical-align: middle;
}

/** or using the class .mat-icon */
.custom-class .mat-icon {
    vertical-align: middle;
}

HTML:

<div class="custom-class">
   <mat-icon>home</mat-icon>
   <span>Some text here 1</span>
</div>