I've been using the 'glide' ring on my Garmin Pilot app. You plug in the glide ratio from the POH and a fudge factor( suggested 20%), it will give you a ring(cyan) showing how far you can glide. Anyway, I'm always surprised at how much less I can actually glide vs what I had previously thought I could. The photo is just south of JFK at 6k( usual transit altitude).