Where can I find (or how can I calculate) the glide ratio for a PA-28-181? I'm filling out ForeFlight's new glide slope feature, and I'm trying to find the glide ratio for a Piper Archer II (PA-28-181). I know the best glide speed is 76, but can't find the glide ratio. Any help on where to find this? 

Edit: 

Below is the glide range graph from my PoH, and below that is the information ForeFlight is asking for. I'm not really sure how to read that graph to get a glide slope number.
If you were to take off from an airport at 2,000' ASL on a standard day, and climb to 7,280' ASL you would be exactly 5,280' above the ground which means exactly 1 statute mile above the ground. 

If you were to cut the engine, and then use the information available in the chart, you should be able to glide about 10 statute miles which yields about a 10 to 1 glide ratio.