sorry...but whatever reason, those calculations just threw me for a loop.Always use a measuring wheel. No reason to risk leaving money on the table. New install of mulch is 1yd.= 80 sq. ft. That is 6-8in. deep, recommended by most nurseries for new plants. top dress, 1yd.=120 sq. ft. at about 4in. deep.
Hope this helps.
You can buy a small one at Home Depot for 20 or 30 bucks.thats what I would like to do but they are so expensive