angular/material2 mat-spinner resize
With the latest update you should use the diameter property:
<mat-spinner [diameter]="70"></mat-spinner>
The diameter represents the amount of pixels for both the width and the height of the spinner. In this case it has a size of 70x70 pixels.
See the following stackblitz example:
https://stackblitz.com/edit/angular-material2-progress-spinner
here is the answer :
<mat-spinner mode="indeterminate" style="margin:0 auto;" [diameter]="30"></mat-spinner>