Let's see .... Area of a circle = pi * radius squared or pi/4 * diameter squared.
diameter . . . . ~area in . . . . . . . cubic feet
of circle: . . . . . .square feet . . . . if 1" deep
4' . . . . . . . . 12.5 sq.ft. . . . . . . . . . ~1 cu.ft.
5' . . . . . . . . 20 sq.ft. . . . . . . . . . . . ~ 1.7 cu.ft.
6' . . . . . . . . 28 sq.ft. . . . . . . . . . . ~2.3 cu.ft.
7' . . . . . . . . 38.5 sq.ft. . . . . . . . . ~3.2 cu.ft.
1" deep means 1/12th of a foot. So divide the "square feet" by 12.
(Actually, mulch several inches deep sounds better to me than just one inch. As long as you don't lay mulch right up against the bark, more is better, isn't it?)
I admit, I don't know anything about cedar bark. With pine bark, I want a layer that is at least 2-4 shreds of bark deep. And COARSE chunks, for mulch.
