Enter the width, length, and thickness of your job, and click on whether you are measuring the depth in feet or inches.

Next, click on either SAND or STONE, or enter a custom density selection (Enter 3000 for gravel).

The SAND and STONE selections will fill in the density of the rock for you; the Custom selection allows you to enter a unique density in the Density field (Careful! If you click on Custom you need to write over the density that was there previously).

Finally, click on the Calculate button. The calculator will estimate the number of tons of material that will be required.

Please note that densities will vary somewhat between different loads, but the default values assigned for Sand and Stone should give you a good estimate.