Johns Lake is a popular hike, being fairly flat and located in a busy part of Glacier National Park near large campgrounds and the Lake McDonald Lodge. There are parts of it that are very nice, but overall there are better hikes to choose from in the park.
The Johns Lake Loop really consists of two separate trails that can be connected via roads to form a loop. The trail can be started either at the John’s Lake Trailhead right on Going-to-the-Sun Road one-tenth of a mile before (when traveling east) the left turn for the Lake McDonald Ranger Station or from the Upper McDonald Creek Trailhead about a quarter mile up the road to the ranger station. The roads that connect these two trailheads complete the loop at this end. At the far end of the loop, there is a very short section of Going-to-the-Sun Road that must be taken to connect the Johns Lake Trail with the Upper McDonald Creek Trail.
Starting from the trailhead on the Going-to-the-Sun Road, the trail climbs a little bit for about a half mile to Johns Lake. This is a pretty little lily pad-covered pond with a great view of Stanton Mountain behind it. The trail continues through thick lodgepole pine woods until it comes out Going-to-the-Sun Road. There is a crosswalk here, and a right turn leads in 100 feet or so to the continuation of the trail down to the footbridge crossing McDonald Creek. This is a great place to enjoy the water and the beauty of the creek. After crossing the bridge, a left turn returns down Upper McDonald Creek Trail past McDonald Falls to the other trailhead. It is about a half mile along the roads to return to the Johns Lake Trailhead.
A better hiking option in this area is to do the Upper McDonald Creek Trail out and back and skip the Johns Lake side of the loop. This route offers much better views and the wonderful sound of the creek for most of the hike.