app/node_modules/@angular/material/toolbar/_toolbar-variables.scss

// Minimum height for toolbar's in the highest density is difficult to determine because
// developers can project arbitrary content. We use a minimum value that ensures that most
// common content (e.g. icon buttons) does not exceed the row boundaries in highest density.
$minimum-height: 44px !default;

$height-desktop: 64px !default;
$maximum-height-desktop: $height-desktop !default;
$minimum-height-desktop: $minimum-height !default;

$height-mobile: 56px !default;
$maximum-height-mobile: $height-mobile !default;
$minimum-height-mobile: $minimum-height !default;

$desktop-density-config: (
  height: (
    default: $height-desktop,
    maximum: $maximum-height-desktop,
    minimum: $minimum-height-desktop,
  )
) !default;

$mobile-density-config: (
  height: (
    default: $height-mobile,
    maximum: $maximum-height-mobile,
    minimum: $minimum-height-mobile,
  )
) !default;