How to increase Bootstrap navbar-brand font-size?

Just use font-size: 100px !important; hope this will be helpful for you.

The font-size property specifies the size, or height, of the font. font-size affects not only the font to which it is applied, but is also used to compute the value of em, rem, and ex length units. Demo Try like this

.navbar-brand
{
  font-size: 100px;
}

Absolute keywords and values

.navbar-brand
    {
      font-size: larger;
    }

It accepts the following absolute keyword values:

xx-small

x-small

small

medium

large

x-large

xx-large

h1 {
    font-size: 250%;
}

h2 {
    font-size: 200%;
}

p {
    font-size: 100%;
}

<h1>MyAwesomeCompany</h1>
<h2>MyAwesomeCompany</h2>
<p>MyAwesomeCompany</p>