Step 1: Measure the length and width of the area.

Step 2: Measure the gravel and sand depths.

Step 3: Convert the dimensions to feet if necessary.

Step 4: Calculate the volumes in cubic yards.

Formula for volume: $$\text{Volume} = \frac{\text{Length} \times \text{Width} \times \text{Depth}}{27}$$

Step 5: Convert the volumes to tons based on the material.