4 ft x 80 ft = 320 feet squared.

That's an area, like square feet of weed cloth, it's flat.

You need height to have volume!

4ft * 80ft * __ ft high = ___ feet cubed <<< that's volume

===

1 ft¹ is length, but we write this as simply 1 ft

1 ft² is area

1 ft³ is volume.

===

The way I like to convert to yards is to convert each measurement

Let's say we had 4ft x 80ft x 2 ft high

To convert, multiply each by (1) as (1yd/3feet)

4ft (1yd/3ft) x 80ft (1yd/3ft) x 2ft (1yd/3ft) = ___ yd³

in this example we have 24 yd³

====

If you only have a few inches, you need to convert it to feet first.

e.g. 2 inches

2 inches (1 ft/12in) = 0.166666666666667 ft

then you'd have

4ft (1yd/3ft) x 80ft (1yd/3ft) x 0.166666666666667 ft (1yd/3ft) = ___ yd³

So determine the depth of soil, then use the technique here.

Let the units help work the problem! Jim

You ALWAYS multiply by (1) to do conversions!!!