If you ever sat through a math class in school wondering when you would ever use anything in the real world, today is your lucky day. Sharpen your pencils and get out your calculators.
Use this formula to determine how much stone dust you need for your project:
(L'xW'xH') / 27 = cubic yards of stone dust needed
In the construction world, most materials are measured in cubic yards. Multiply the Length, in feet, by the Height, in feet, by the Width, in feet, and divide by 27. This will tell you how many cubic yards of stone dust you need.
For example, if your patio is 20 feet long and 20 feet wide, and you needed 1 inch of stone dust for the base, you would use the formula like this:
(20'x20'x0.08') / 27 = 1.19 cubic yards
When using this equation, make sure all of your measurements are in feet. Since we needed 1 inch of stone dust, I used 0.08 feet for my height. To convert inches to feet, divide the number of inches by 12. In this case, I divided 1 inch by twelve to get 0.08 feet.
If your number comes out as a fraction, and it probably will, round up. Stone dust and other base materials like crushed stone and sand are usually sold in 0.5 cubic yard increments. In the example above, you would round the 1.19 to 1.5 cubic yards of stone dust. It's better to have a little extra than to run short.