# Formula for how much dirt?

• posted on April 7, 2005, 11:44 pm
I want to create a raised flower bed. Is there a way to figure out how much dirt I will need?
I want the flower bed to be relatively circular, about six feet in diameter, and about six inches deep.
Is there some way to get this dirt without buying a bunch of bags of dirt? In other words, if I go to a nursery or somewhere else, is there someone who will deliver the amount of dirt I want?
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8^)~~~ Sue (remove the x to e-mail)
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• posted on April 7, 2005, 11:57 pm
Suzie-Q wrote:

The volume of a cylinder is: (Pi x radius-squared ) x depth
3.14 x 3 x 3 x 0.5 = a little over 14 cubic feet
So if you're buying 2 cubic foot bags of soil, you'll need 7 bags.
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Warren H.

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• posted on April 8, 2005, 2:44 pm
On Thu, 07 Apr 2005 23:44:48 +0000, Suzie-Q wrote:

A yard will cover 108 square feet at 3" deep. A cubic yard is 27 cubic feet. If you were buying bags of dirt and the bags were 2 cubic feet, then you would need 14 bags.
Most soil suppliers will deliver for a fee and sell in cubic yards. With all things in life though, they won't bring you a cubic yard though, it will be under a bit over over a bit. They just dump it in the truck and go.
You can borrow/rent a full size truck and it will carry a yard.
Good luck to you.
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Yard Works Gardening Co.
http://www.ywgc.com
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• posted on April 8, 2005, 6:20 pm
Timothy wrote:

A formula:
_L' x W' x D"_= cubic yard (s) 324
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Travis in Shoreline (just North of Seattle) Washington
USDA Zone 8b
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• posted on April 8, 2005, 6:51 pm
Travis wrote:

Feet times feet times inches equals cubic yards? Ummm. No.
Yards times yards times yards equals cubic yards (when you're dealing with square corners). More accurately, square yards times height in yards equals cubic yards. Or square feet times height in feet divided by 27 equals cubic yards.
One key to computing area or volume is to have each measurement in the same unit. All feet. All yards. All inches. And then what you get is that unit squared (for area) or cubed (for volume). Mixing unit times gives you a worthless result. A number no better than a random number.
Also, the original poster had a circular bed. The area of a circle is not length times width. It's Pi times square radius. Multiply that by the height in the same unit as the radius to get volume. Again, the measurements must be in the same unit. If the radius is measured in feet, then the height must be in feet, too.
If we were dealing with a triangular area, expand it so that it's a 4-sided area, with one edge going from corner to corner. Now use the same formula as for a 4-sided area, but divide by two.
To convert from cubic feet to cubic yards, you need to remember that a cubic yard is 3-feet by 3-feet by 3-feet. Or put another way, three layers of 3-feet by 3-feet, or 3 layers of 9 cubes, thus 27 cubic feet in a cubic yard.
But whatever formula is used, each measurement must be in the same unit. All feet. All yards. Or all inches. No mixing.
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Warren H.

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• posted on April 8, 2005, 7:58 pm
Warren wrote:

I formatted that incorrectly.
_L'xW'xD"_= cubic yard/s 324
The formula I gave was not as an answer to the OP but just as a general formula.
From: http://www.tcmastergardener.org/html/the_real_dirt_on_austin_area_s.html
How much mulch or soil is needed?
To determine how much mulch is needed for a specific area, measure the area to be covered and use the following formula:
Area to cover (in square feet) x depth of mulch or soil desired (in inches) x 0.0031 = cubic yards of mulch or soil required
-- or use this alternate method -- Area to cover (in square feet) x depth of mulch or soil (in inches) / 324 = cubic yards of mulch or soil required
For example, to cover an area of 100 square feet with 3 inches of mulch: 100 square feet x 3 inches deep x 0.0031 = 0.93 cubic yards needed
Note: If buying mulch in 1 cubic foot bags, multiply the cubic yards needed by 27 (there are 27 cubic feet in 1 cubic yard) to find the number of bags needed.
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Travis in Shoreline (just North of Seattle) Washington
USDA Zone 8b
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• posted on April 9, 2005, 2:49 am
On Fri, 08 Apr 2005 07:44:11 -0700, Timothy

The formula to determine the volume of a cylinder is: Pi * (Radius squared) * height = 3.14 * (3 * 3) * .5 = 14.14 cubic feet.
That's a little more then half a cubic yard. Don't know that they sell half yards, but I've never tried. If that's all I needed, I'd probably just buy 5 3 cubic foot bags, but if you can pick it up yourself it may be cheaper to buy by the yard. I'm sure you can probably put the rest to use somewhere. The soil will also compact and settle somewhat, especially after the first heavy rain, so you may need a little more then the original estimate.
Swyck