Wonder how much good stuff you need?
To find how much you need, just multiply the surface area by the depth of your container (e.g. basket, bed, garden, lawn). Remember to keep it all in the same unit. For instance if your bed is only 6'', use 0.5 ft! There are 27 cu ft in a cubic yard, and 1000 L in a cubic meter.
Here is a great tool to help you with volume calculations for simple shapes (e.g. square, rectangular):
Here is another great too that can help with volume calculations for more complex shapes (e.g. triangle, circle):https://www.calculatorsoup.com/calculators/construction/cubic-yards-calculator.php
And here is a nifty gadget that can help you determine the surface area of an irregular shape (e.g. backyard):