**Calculator for Drain Rock / Sand Material**

The following formula gives you an estimate of the amount of material you may need to do a project using the following materials: 1 1/2″ x 3/4″ Round Rock, 3/4″ x 1/4″ Round Rock, 3/8″ Pea Rock, Sand, 1 1/2″ x 3/4″ Crushed Drain Rock, or 3/4″ x 1/4″ Crushed Drain Rock.

First, multiply Length x Width x Depth, in feet, to get the total Cubic Footage. Next take the total Cubic Footage result and divide it by 27 to get your total Cubic Yards. Then take your total Cubic Yards result and multiply it by 1.30 to find the estimated tonnage needed for your project. Compaction is not a factor in this equation because drainage materials do not have a compaction component.

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**Calculator for Horse Arenas / Round Pens**

The following formula gives you an estimate of the amount of material you may need to do a project for a Horse Arena or a Round Pen using any of the above mentioned materials:

To figure a circle, using feet, split the circle in half and multiply the two halves together, multiply by 3.14 and multiply by Depth in feet (Example: 60′ circle would be 30′ x 30′ x 3.14 x the Depth) this will give you your total Square Cubic Footage. Next, take your total Cubic Footage and divide it by 27 to get your total Cubic Yards.

If you are using rock with fines, then you take your total Cubic Yards and multiply it by 1.33 to find the estimated tonnage needed for your project. Once again, to include compaction as a component, multiply your estimated tonnage once more by 1.33 for the an estimated project tonnage.

For Drain Rock / Sand Material, take your total Cubic Yards number and multiply it by 1.30 to find the estimated tonnage needed for your project. Once again, Compaction is not a factor in this equation because drainage materials do not have a minus component.

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## Depth Conversion Chart

2″ = .17 ft

3″ = .25 ft

4″ = .33 ft

5″ = .42 ft

8″ = .66 ft

9″ = .75 ft

10″ = .83 ft

11″ = .92 ft

12″ = 1 ft