Making a Good Estimate For Your Outdoor Garden Space


Guess-work can be scary


Here are some quick tips to save yourself time and money when determining how much landscape rock to purchase for your landscape design. 

Look at the shape of your project and take a few simple measurements. Use this information to calculate the square footage as best as you can. Your estimate doesn’t have to be perfect, you just need to get a general idea of the area of your project. In some cases, you may need to purchase 10-15% more than you calculated in order to accommodate odd stone sizes, or the need to cut stone pieces down to fit your pattern.

Remember, always measure in feet! As interesting as it is to know the square inch-age, or the square meter-age of your project, stone area-coverage is almost always described in square foot-age.

Squares and Rectangles

Area = Length x Width

There is nothing uncool about being a square--or rectangle for that matter. Squares and rectangles have the easiest calculation! Even if your space isn’t perfectly rectangular, measuring the length and width, multiplying the two, and giving yourself a pat on the back is a much better reward than hours of intricate math to get a few square feet more precise.

Use this method for garden pathways. Whether it’s straight or twisted, a simple length and width measurement will get the job done.


Area = ½ Length x Height

Historically, the triangle has been a symbol of power and strength, and is a great dynamic shape for any project. To get the square footage of your powerhouse project, measure the longest side of the triangle and measure from point straight down to the longest side of the triangle. Take half of the base length, multiply it by the height, and give yourself a pat on the back.

Circles and Semi-Circles

Area = 3.14 x Radius2

If you’re working on a circle, be reassured that some of the best things in life are round. Pizzas. Hamburgers. Cookies. Cakes. Analogue clocks pointing to lunch time.

Whether perfectly circular, mostly round, or just roundish, all you need to measure is the distance from the center to any edge and multiply that distance by itself. Then, multiply it by 3.14, and give yourself a pat on the back--or a slice of pie.

If you have a half circle, just use the same formula and divide the result in half. Piece of cake!

Free-Form Areas

If imprecise measurements would keep you up at night you can get more complex to determine a more exact area. An easy trick is to divide up your free-form space into smaller, more geometric pieces. Use the formulas from above and add the square footage for each section together.


What about measurements for depth? If you are laying down patio stone, you only need to dig down far enough to lay a bed of sand for the stone. Don’t forget to factor in the thickness of your flagstones. For more on laying patio stones, see our article on building a beautiful garden path. When putting down decorative ground cover stone such as crushed rock, volcanic rock, or gravel, you’ll want to account for 2-inches of depth for stones up to 2-inches in size. For 3-inch ground cover stone, you’ll want a depth of 3-inches. This means that one square foot of space will require either 2 to 3 inches deep of stone.

Once you’re finished, bring that estimate with you to the stone yard and you are on your way to the most beautiful yard on the block.

Making Your New House a Home