Question
Hello, I have finally decided on using landscape stones instead of mulch to dress up my landscaping.  However, I'm am wondering if you would know the most inexpensive way to do this.  How do I estimate how many rocks I need? I would like to do the entire perimeter of my home as well as some 'island' areas in front and around my shed. Please help!

Answer
Hi, Mica-

Here is a web location that shows you pictures of rock mulch and how much will generally cover the area in question:

http://www.lawnkingnursery.com/rock.html

Rocks are very local, so not all shown are available in your area, or you may have even BETTER ones that you can use.  I'd suggest a minimum of 3 inches thick.

On to the math:  Area = length x width.  For example, if you have 300 square feet (30 ft x 10 ft, 60 ft x 5 ft, 14 ft square, or some other configuration), and you want to cover the surface with 3" of rock, you'll need 300/70*, or 3 cubic yards of material.  

For islands (I am assuming a circle shape), the area formula is 2 x pi x the circle's radius.  For a circle 20 feet wide, that would be 2 x 3.14 x 10 ft = 62 square feet.  With a mulch 3 inches thick, you抣l need  62 sf/70* or 1 yard of rocks (.89 actually, but most landscape materials yards sell in no smaller quantity than ?yard)

* With rocks, its better to over-estimate slightly ?If you did a little additional math, 3?of cover should actually be 108 s.f., and not 100 or 70, as in the two links above & below.  Before you (and other readers) get upset with me, I am aware the two sites disagree.  For smaller residential projects, these differences are within acceptable variation (+/- ?yard).

If math just isn抰 your thing, here is the other website that will calculate it for you, if you know your square footage and mulch depth:

http://www.gotmulchpa.com/calculator.php

To aid in measuring landscape areas, I find using a wheel-measurer is indispensible - I keep one in my car for job sites and they are only about $20.

The worst way to buy landscape rocks is by 揵ags??One; they are more expensive that way, and Two; most folks cannot convert cubic feet to cubic yards easily (9 bags @ 3 cubic feet = 1 cubic yard).  They are easier to move by yourself (i.e. without a wheel burrow), but you pay for the convenience in higher cost, in my opinion.

Now, if your local supplier sells landscape rocks in "tons" instead of "yards", the material weight is different than its volume. 1 cubic yard of dry rock mulch is about 2,250 pounds (1.125 tons) You will lose about 13% on the covering ability, by purchasing rocks by the ton.  For small residential landscapes, 1 ton GENERALLY = 1 yard of material.   

Rock weight can vary by density & moisture.  Thankfully rocks don抰 hold a lot of water, but there are enormous differences in weight between volcanic stone versus granite chips.

I would also suggest you use landscape/weed fabric under the rock (NOT black plastic, which will kill trees & plants!) to slow the progress of future weed outbreaks and aid in weeding those that do come up.

Hope it helps. ~Marc

PS; Are you Canadian?  My apologies, as I did all the calculations in inches/feet, and not metric!!  If so, 1 cu. Yard =  0.7646 cu. meter

~M