Everyone's "formula" for mulch is probably different, based on thickness put down, type and amount of plant material in bed. That said... I usually figure 240 sq.ft. per cu.yd. of mulch. Measure a few of your own jobs and you'll come up with a number that works for you. My figures are based on shredded hardwood mulch, 2-3 inches thick.
13 yds how do you figure that? That's almost four inches of mulch over that 1400s.f. area. To answer your question simply.
Divide your s.f. by 162 = yds. for a two inch thickness of mulch.
Ex: 1400/162= 8.64yds. spread @two to three inches.
With the fluff factor of mulch (when loading and spreading mulch is fluffed full of air) you can usually purchase about 15% less and still cover the area with two to three inches of fluffed mulch. I'd say count on buying seven for this job.
Well acutally, it was four inches. Just check the middle figure of mine. 1400 sq ft * .25 ft = 350 cu ft 350 cu ft / 27 cu ft per cu yd = 13 cu yds.
If you want less you can do 1400 sq ft * (inches of mulch)/12 = x cu ft / 27 cu ft per cu yd = y cu yds
We did this one before. Just keep in mind the "fluff" factor mentioned in the other posts. Also, guntruck didn't tell us what thickness he was going to use, so all of the suggestions were mostly correct, for that thickness. (Actually Vandora gave the calculation for 3 inches of depth) http://www.lawnsite.com/showthread.php?threadid=3997
Don't let math stand in your way. It's to complicated to figure out square footage and divide it by 162. Why even bother with 1yd/100s.f., why not just look at the job while in your truck and guesstimate. They have these new inventions, when numbers are put in correctly they figure out mathematical equations for you, they're called calculators.
Ok wait a minute, if Vandoras calc. came out at 4" coverage w/13 yards and you figure your calc. @3" per yard how do you come up w/ only 7 yards? That's a hell of a fluff factor<img src="http://dirtrider.net/ubb2/biggrin.gif">
Actually i don't measure it off i just walk and look, can't do it from the truck yet though, still working on that