How to fix uneven padding in a button - css

Question

This is an insanely basic question but for the life of me I can't figure it out. I'm creating a button class and no matter what I do, there's extra space to the bottom and right of the text.
Tried altering line-height, border-box, margins, display, text-align and some others.
.button {
font-family: 'helvetica';
font-size: 16px;
color: #000;
margin: 0px;
position: relative;
letter-spacing: .4em;
text-transform: uppercase;
text-decoration: none;
color: $secondary-color;
border: 4px solid #000;
padding: .3em .75em;
margin: 0px;
text-align: center;
display: inline-block;
transition: all .25s ease-in-out;
-moz-transition: all .25s ease-in-out;
-webkit-transition: all .25s ease-in-out;
}
.button:hover {
color: #fff;
background-color: #000;
}
project
Just trying to get an evenly padded button that will resize to the text content.

Answer 1

this is happening because of letter-spacing:0.4em on your last letter to remove this wrap last letter in span with letter-spacing:0 like this:
.button {
font-family: 'helvetica';
font-size: 16px;
color: #000;
margin: 0px;
display:inline-block;
align-items:center;
position: relative;
letter-spacing: .4em;
text-transform: uppercase;
text-decoration: none;
border: 4px solid #000;
padding: .3em .75em;
margin: 0px;
text-align: center;
transition: all .25s ease-in-out;
-moz-transition: all .25s ease-in-out;
-webkit-transition: all .25s ease-in-out;
}
.button:hover {
color: #fff;
background-color: #000;
}
projec<span style="letter-spacing:0px;">t</span

Answer 2

Although the spec says letter-spacing shouldn't be added at the end of the line, it seems it is added regardless. You can use this padding instead to "undo" it:
padding: .3em calc(.74em - .4em) .3em .75em;
or equivalently
padding: .3em .35em .3em .75em;
.b1 {
border: 1px solid black;
padding: .3em .75em;
letter-spacing: .4em;
}
.b2 {
border: 1px solid black;
padding: .3em calc(.75em - .4em) .3em .75em;
letter-spacing: .4em;
}
<span class="b1">FOO</span>
<span class="b2">FOO</span>