Google Maps v3 getBoundsZoomLevel

HTML

<script src="http://maps.googleapis.com/maps/api/js?sensor=false&amp;dummy=.js"></script>
<div id="mapDiv" style="width: 500px; height: 375px; border: solid 2px #666;">
</div>

JavaScript

// Change this array to test.
var points = [
    { lat: 36.170603, lng: -114.577065 }
];

function getBoundsZoomLevel(bounds, mapDim) {
    var WORLD_DIM = { height: 256, width: 256 };
    var ZOOM_MAX = 10;

    function latRad(lat) {
        var sin = Math.sin(lat * Math.PI / 180);
        var radX2 = Math.log((1 + sin) / (1 - sin)) / 2;
        return Math.max(Math.min(radX2, Math.PI), -Math.PI) / 2;
    }

    function zoom(mapPx, worldPx, fraction) {
        return Math.floor(Math.log(mapPx / worldPx / fraction) / Math.LN2);
    }

    var ne = bounds.getNorthEast();
    var sw = bounds.getSouthWest();

    var latFraction = (latRad(ne.lat()) - latRad(sw.lat())) / Math.PI;
    
    var lngDiff = ne.lng() - sw.lng();
    var lngFraction = ((lngDiff < 0) ? (lngDiff + 360) : lngDiff) / 360;
    
    var latZoom = zoom(mapDim.height, WORLD_DIM.height, latFraction);
    var lngZoom = zoom(mapDim.width, WORLD_DIM.width, lngFraction);

    return Math.min(latZoom, lngZoom, ZOOM_MAX);
}

function createMarkerForPoint(point) {
    return new google.maps.Marker({
        position: new google.maps.LatLng(point.lat, point.lng)
    });
}

function createBoundsForMarkers(markers) {
    var bounds = new google.maps.LatLngBounds();
    $.each(markers, function() {
        bounds.extend(this.getPosition());
    });
    return bounds;
}

var $mapDiv = $('#mapDiv');

var mapDim = {
    height: $mapDiv.height(),
    width: $mapDiv.width()
}

var markers = [];
$.each(points, function() { markers.push(createMarkerForPoint(this)); });

var bounds = (markers.length > 0) ? createBoundsForMarkers(markers) : null;

var map = new google.maps.Map($mapDiv[0], {
    center: (bounds) ? bounds.getCenter() : new google.maps.LatLng(0, 0),
    mapTypeId: google.maps.MapTypeId.ROADMAP,
    zoom: (bounds) ? getBoundsZoomLevel(bounds, mapDim) : 0
});

$.each(markers, function() { this.setMap(map); });