Use jQuery to calculate the heights of each row in a list, and the total number of rows (even if the list items are floated)

pilau-list-dimensions.js

/**
 * For a list, calculate how many rows, height of each row
 *
 * @param	{object}	l	The list jQuery object
 * @return	{object}
 */
function pilau_list_dimensions( l ) {
	var d = {
		row_heights: []
	};
	var lis = l.children( 'li' );
	var r = 1; // row
	var llio; // last li offset
	var lih; // li height
	var rh; // row height (highest li)

	// Go through every li
	lis.each( function( i ) {
		var el = jQuery( this );
		var elo = el.offset();
		var lih = el.outerHeight( true );

		if ( typeof llio == 'undefined' ) {

			// First iteration
			rh = lih;

		} else if ( elo.top > llio.top ) {

			// This element is lower than the last one - we're on a new row
			r++;
			d.row_heights.push( rh );

		} else {

			// Pass li height through as new highest li in row?
			if ( lih > rh ) {
				rh = lih;
			}

		}

		// Pass this element's offset through
		llio = elo;

	});

	// And the last row...
	d.row_heights.push( rh );

	// Add total number of rows
	d.row_count = r;

	return d;
}