FORMULAS FOR AGGREGATES SIMPLIFIED


With the proliferation of online aggregate calculators and other tools available to simplify construction material estimates our team thought to share the basic logic and formulas that drive these calculations:

When we talk about a yard of gravel or a yard of sand, we’re referring to a cubic yard. If stacked neatly, it would form a cube that is 3' wide by 3' long by 3' deep. Whether you’re talking about gravel or sand or river rock or mulch or soil, a yard of material is always 27 cubic feet (3 x 3 x 3). So it’s easy to estimate how many yards of material you need by calculating the volume of the space you need to fill and dividing by 27. 

For example:

(Area of the space to be filled (l x w) x Desired depth of material*) ÷ 27 = # of yards needed

**Be sure to use "feet" as the unit of measurement for all calculations.**

Decorative Aggregates

Using the formula above, you can calculate the quantity required as long as you know the length, width and depth of the space you need to fill. But how deep is deep enough?

Decorative aggregates vary greatly in size. The larger the stone, the thicker it needs to be applied to achieve full coverage. This simple formula calculates the minimum depth required for any stone:

Diameter of the stone* x 1.6 = required depth (in inches) to achieve coverage

*In this formula, be sure to use "inches" as the unit of measurement.

Let's say we're constructing a dry riverbed that is 3' wide by 20' long and we’re going to line it with washed granite that varies in size from 4" to 6". The first step is to calculate the required depth using the average diameter of the stone:

5" x 1.6 = 8" or 0.67'

So we know that we have to lay the granite 8" (or 0.67') thick in order to fully cover the bottom of the riverbed. Next, we figure out how many yards of washed granite we need:

(3' x 20' x 0.67') ÷ 27 = 1.49 yards

In turn, we'll need 1½ yards of washed granite for our dry riverbed project.

Construction Aggregates

Earlier, we mentioned that a yard of any material is always 27 cubic feet but there’s an exception to every rule. As base material is compacted  it condenses and fills less space than it did before compaction. How much less depends on the level of compaction and the material being compacted but 20% is a good rule of thumb. When ordering material that will be compacted, don’t forget to bump up the quantity to account for this loss. There are tons of online calculators that will do this for you – if you find one that works for you, bookmark it for use whenever you need it.

Screened Sand

Concrete and Mason sands are very fine sand that are mixed with cement to produce mortar for building projects. When using Type S or Type N cement, the ratio of brick sand to cement is 3:1. Just in case math wasn’t your favorite subject, here are the basics:

  • ½ yard of brick sand requires 5 to 6 bags of Type S or Type N cement
  • 1 bag of Type S or Type N cement requires 3 to 4 poly bags of brick sand

... and there you have it – aggregate estimating made easy. If you need a hand, you can always give us a call. We have a variety of construction and decorative aggregates available for your convenience and are happy to help you determine how much you'll need!