How to figure how much bulk material you need

Rectangle - Length x width x depth - divided by 27 = cubic yards
Example:  10 ft x 10 ft x .5 ft (6 inches) divided by 27 = 1.85 cubic yards
 
Triangle - Length x width x .5 = square feet
Example:  10 ft x 10 ft x .5 = 50 sq ft
Use conversion chart below (square feet to cubic yards)
 
Circle - Radius (1/2 the diameter) squared x 3.14 = square feet
Example:  10 ft radius squared (10 ft x 10 ft = 100 ) x 3.14 = 314.0 sq ft
Use conversion chart below (square feet to cubic yards)
 
Conversion Chart (square feet to cubic yards)
1 yard covers at a depth of:
1/4" deep - 1296 square feet
1" deep - 324 square feet
2" deep - 162 square feet
3" deep - 108 square feet
4" deep - 81 square feet
12" deep - 27 square feet
 
Volumes
Heaping load on a full size pickup is about 3 cubic yards
Max load on a small pickup is about 1 1/2 cubic yards
Most full size pickups can carry 1 cubic yard of topsoil or stone (which is very heavy)
Small single-axle dump truck load is 5 yards
Big dump trucks are 10 to 15 yards
27 cubic feet in one cubic yard is 3' x 3' x 3'
One cubic yard = 9 square feet (3' x 3')
There are 21 bushels in one cubic yard
 
Recommended Depth of Materials
Topsoil in lawns - minimum 4"
Lawn topdressing - 1/4"
Garden soil in flowerbeds - 6-12"
Bark mulches - 3"
Stone less than 1" in diameter - 3"
1 1/2" Riverstone - 4"
3-6" Stone - 6"
Pathways - 4"
 
Miscellaneous Hints
Be careful when using a wood mulch around your house because it is a food source for termites and other bugs. Use bark products instead. Bark is a trees natural protection from these pests.
 
Try to avoid watering your lawn at night especially late night. The best times to water are as follows (best to worse): mid-day, morning, evening then night. Frequent light waterings are best, over-watering and watering at night help promote disease.
 
"If you're building a patio, make sure it is big enough", says landscape architect Paul Maue. "Getting the scale right is the hardest thing - you always need more space than you think." Try setting up a table and chairs on the lawn first to see how much room you need. Maue's rule of thumb: allow 25 square feet per person for a chair and room to move.