How Much Do Stones Weigh?
How Many Pounds of Stone Will I Need?
It is very easy to estimate the amount of stone needed if you know the size of the jar and how much the stones weigh in pounds per cubic inch.
This works for small projects such as filling a planter, but it can also be used for estimating how many tons of stone will be needed in a landscaping project.
Planter: An Easy Example…
Let’s say that you have some nice planters like the three in the image at right. Each planter has a soil surface area that is nine inches long and nine inches wide. You want to cover the soil surface about two inches deep with mixed tumbled stones. How many pounds will you need?
Your first job is to calculate how many cubic inches of stone will be needed. This is done by multiplying length x width x depth.
Great! We need 162 cubic inches of stone. How many pounds is that?
Mixed tumbled stones weigh about 0.0618 pounds per cubic inch (or about 107 pounds per cubic foot), and we need 162 cubic inches, so we simply multiply…
There’s our answer. We need about 10 pounds of mixed tumbled stones for each planter. This number is an estimate and it should be fairly close. However, depending upon the size of the stones and the shape and the size of the container in which they will be used, that number could be a little high or a little low. But, it is a reasonable estimate.
Round Flower Pot
The amount of stones needed to cover the surface of a round flower pot can easily be calculated. As an example, how many pounds of stone would be needed to cover the soil surface of the flower pot at right to a depth of about 1 1/2 inches?
Our first task is to calculate the soil surface area. The formula for calculating the area of a circle is A = Pi x r2. Pi is equal to approximately 3.14 and our flower pot has an inside radius of 4 inches (a diameter of 8 inches). So by calculation, the surface area is…
If we multiply the surface area by the desired depth of coverage the result will be the volume of stones needed.
Now to get the weight of the stones needed, we multiply the volume by the density of the stones (0.0619 pounds/inch3).
So, we will need about 4.66 pounds of stone to cover the soil in our flower pot to a depth of about 1 1/2 inches.
Much Larger Projects…
This same method of calculation can be applied to landscaping projects where rounded river stone is used. Since these are much larger projects we will use pounds per cubic foot for the weight of the stone. Most rounded river stones weigh about 100 pounds per cubic foot.
Let’s say that we want to have a bed of shrubbery along the front of our home which is 85 feet long. And, we want that bed of shrubbery to be 5 feet wide and covered by a layer of river stone 4 inches deep. First, we calculate how many cubic feet of stone are needed by multiplying the length of the bed by its width and by the depth of the stones…
Then multiply by volume of stone needed by the density of the stone – which is 100 pounds per cubic foot.
You can see that we will need about 14,025 pounds of stone or a little over 7 tons.