How do I calculate the amount of pebbles to buy?

[#1]

To calculate the volume of stones needed to fill an area, use the formula for the volume of a rectangular prism: Volume = length × width × depth. 

For example, to cover an area of 3.5 meters by 5 meters up to a depth of 30 millimetres (0.03 meters), the calculation is: Volume = 3.5 × 5 × 0.03 = 0.525 cubic meters. Therefore, you would need 0.525 cubic meters of stones to fill the area.

The size of the stones affects the coverage and appearance but does not change the overall volume calculation. However, consider that smaller stones (10 to 15 mm) may pack more tightly than larger stones, potentially requiring a bit more volume to cover the same area if there's less air space between them.

Ensure that the stones are evenly spread to maintain the same depth across the entire area. - EricL