You can estimate the materials needed to build a stone wall using simple algebra. You need to determine the dimensions and the type of stone wall you want to build before you can proceed. Determine the height, width and length of the wall. You also need to decide whether you are going to build a dry stack or a wet stack wall. The wet stack wall uses mortar between the rocks or stones to add additional strength to the wall.

## Determine Stone Volume

## Step 1

Determine the length of the stone wall in feet.

## Step 2

Calculate the wall width. Rock wall width should always be 2/3 of the wall height. Use this formula to calculate the wall width: Y = 2/3X; where X = wall height, Y = wall width; For example, if a rock wall is 3 feet high, the width should be 3 x 2/3 (or .666) = 2 feet.

## Step 3

Calculate the total volume of stone needed by using the formula: length x width x height = volume in cubic feet. For example, if the wall length is 30 feet, the width is 2 feet and the height is 3 feet. The volume of the wall is 30 x 2 x 3 = 180 cubic feet.

## Step 4

Calculate the tonnage of rock needed by converting the cubic foot volume into tons. Use the standard formula of 15 cubic feet of rock = 1 ton of rock. Divide the total cubic foot volume of rock by 15 to determine the number of tons of rock to purchase. For example, 180 cubic feet of rock divided by 15 = 12 tons of rock to complete a 30 x 2 x 3 foot wall.

## Dry Stack Material Volume

## Step 1

Determine the volume of gravel needed for a dry stack stone wall foundation using the formula: length x width x height = volume in cubic feet. The stone wall foundation requires a 4-inch bed of gravel. For example, if the wall is 30 feet long, the width is 2 feet and the height is 4 inches (or 1/3 of a foot, or .333 feet). The volume of gravel needed for the foundation of the dry stack stone wall is 30 x 2 x .333 = 20 cubic feet.

## Step 2

Determine the volume of gravel needed for the wall portion of a dry stack stone wall using the formula; length x width x height divided by 3 = volume in cubic feet. A dry stack rock wall uses gravel to fill gaps between the rocks in the wall. For example, if the wall length is 30 feet, the width is 2 feet and the height is 3 feet, the volume of gravel needed to construct this wall is 30 x 2 x 3 = 180 divided by 3 = 60 cubic feet.

## Step 3

Determine the total amount of gravel needed to construct a dry stack rock wall by adding the amount needed for the foundation and the amount needed for the wall. For example, 20 cubic feet of gravel is needed for the foundation, and 60 cubic feet of gravel is needed for the wall. The total amount of gravel needed for this wall is 80 cubic feet of gravel.

## Step 4

Calculate the tonnage of gravel needed by converting the cubic foot volume into tons. Use the standard formula of 15 cubic feet of gravel = 1 ton of gravel. Divide the total cubic foot volume of gravel by 15 to determine the number of tons of gravel to purchase. For example, 80 cubic feet of gravel divided by 15 equals 5.333 tons. You will need to order 6 tons of gravel for this wall.

## Wet Stack Material Volume

## Step 1

Determine the volume of gravel needed for a wet stack stone wall foundation using the formula: length x width x height = volume in cubic feet. The stone wall foundation requires a 4-inch bed of gravel. For example, if the wall is 30 feet long, the width is 2 feet and the height is 4 inches (or 1/3 of a foot, or .333 feet). The volume of gravel needed for the foundation of the wet stack stone wall is 30 x 2 x .333 = 20 cubic feet.

## Step 2

Calculate the tonnage of gravel needed by converting the cubic foot volume into tons. Use the standard formula of 15 cubic feet of gravel = 1 ton of gravel. Divide the total cubic foot volume of gravel by 15 to determine the number of tons of gravel to purchase. For example, 20 cubic feet of gravel divided by 15 equals 1.333 tons. You will need to order 2 tons of gravel for this wall.

## Step 3

Determine the number of bags of mortar mix needed to complete a wet stack rock wall by using the formula: 1 bag of grout for every 5 cubic feet of rock wall. Divide the total cubic feet of the rock wall by 5 to determine the number of bags of mortar required to complete the wall. For example, a 180 cubic foot rock wall divided by 5 equals 36 bags of mortar mix.

## Step 4

Calculate the amount of sand required to add to the mortar mix. Equal amounts of sand and mortar mix are combined with water when making mortar. Each bag of mortar mix weighs 100 pounds. Use the formula: 100 pounds of sand for each bag of mortar mix. For example, 36 bags of mortar mix will require 3,600 pounds of sand. You will need to purchase 2 tons of sand to build this wall.

### Tip

Estimate materials by rounding up to the nearest whole number when you calculate. It is better to have more material than not enough to do the job.

#### Fred Howe

Fred Howe, a writer since 2009, holds a B.S. in sociology from George Fox University. A retired correctional officer from Pelican Bay State Prison in California, Howe has also worked as a sous chef and catering manager.