How do I center my navigation bar?

I’ve been trying to do this on my own but have had no success. I want to simply center my site’s navigation bar, not have it aligned left or right. I need it center aligned and horizontal. Any tips? Below is my CSS code for the navbar – what should I change?

/*
navigation
---------------------------------------------- */

ul#nav {
float: right;
font-size: 0.9em;
text-align: right;
text-transform: uppercase;
letter-spacing: 0.1em;

}
#nav li {
float: left;
list-style-type: none;
display: block;
margin-left: 10px;
}
#nav li a {
float: left;
height: 100%;
display: block;
padding: 30px 5px 0;
}
#nav li a:hover,
body#home li#nav-home a,
body#archives li#nav-archives a,
body#contact li#nav-contact a,
body#about li#nav-about a {
background: #f9f9f9;
}