how to increase size of mdi icons code example

Example 1: mdi icon size and color

<div class="input-group">
    <input type="text" class="form-control" placeholder="Search...">
    <span class="input-group-btn">
        <button class="btn btn-default" type="button" aria-label="Search">
            <i class="mdi mdi-magnify" aria-hidden="true"></i>
        </button>
    </span>
</div>

Example 2: mdi icon size and color

<div class="input-group">
    <span class="input-group-addon">
        <i class="mdi mdi-tag" aria-hidden="true"></i>
    </span>
    <input type="text" class="form-control" aria-label="Tag">
</div>