Basic Formulas
The formulas provided are approximate and Dakota Hardscape Supply can not be held responsible for any miscalculations
Converting Inches to Tenths of Feet
1 divided by 12 = .084 | 7 divided by 12 = .584 |
2 divided by 12 = .167 | 8 divided by 12 =.667 |
3 divided by 12 = .25 | 9 divided by 12 = .75 |
4 divided by 12 = .334 | 10 divided by 12 = .834 |
5 divided by 12 = .417 | 11 divided by 12 = .917 |
6 divided by 12 = .5 | 12 divided by 12 = 1 |
Square Footage of a Circle
- Radius x Radius x 3.14 = Area
- Example: Radius = 10 ft
- 10 X 10 = 100 X 3.14 = 314 Square Ft.
Square Footage of Rectangular Shapes
These shapes are defined by the opposite sides being straight, parallel, and of equal length. The area of all 3 shapes is found by multiplying the length (L) times the width (W).
Square Footage of a Triangle
Consider the longest side of the triangle the base.
Measure a perpendicular line from the opposite angle to the base to determine the triangle's height.
Multiply the base by the height, and divide that number in half to determine the area.
Square Footage of an Oval
The area of an oval is found by multiplying the width (W) times the length (L), then multiplying the result by 0.8
Square Footage of Pentagons, Hexagons & Octagons
Square Footage of a Pentagon (5 Equal Sided Shape)(Length of 1 Side)² x 1.7
Square Footage of a Hexagon (6 Equal Sided Shape)(Length of 1 Side)² x 2.6
Square Footage of a Octagon (8 Equal Sided Shape)(Length of 1 Side)² x 4.84
Square Footage of a Trapezoid
The area of a trapezoid is found by first finding the average length of the parallel sides (A + B) / 2, then multiplying the result times the height (h).
Compound Simple Shapes
Many landscape areas can be sub-divided into multiple, simple shapes. In these cases, use the formulas for the simple shapes and add the results for the total square footage. See the appropriate formula in other sections of this article
Odd Shapes
The method used for irregular shaped areas is called the "offset method". First measure the length of the longest axis of the area (line AB). This is called the length line. Next, divide the length line into equal sections, for example 10 ft. At each of these points, measure the distance across the area in a line perpendicular to the length line at each point (lines C through G). These lines are called offset lines. Finally, add the lengths of all offset lines and multiply the result times the distance that separates these lines (10 ft. in this example).
- Length line (AB) = 60 ft., distance between offset lines is 10 ft apart
- Length of each offset line:
- C = 15ft, D = 10ft, E = 15ft, F = 25ft, G = 20ft
- Total length of offset lines = C(15) + D(10) + E(15) + F(25) + G(20) = 85 ft
- Area = Distance between offset lines(10ft) x sum of the length of the offset lines(85ft) = 850 Square Feet
Sand, Gravel and Dirt
Length x Width x Depth Divided by 27 = Cubic Yards x 1.35 = Tonnage x 1.33 = Compacted Tons
LENGTH X WIDTH = SQUARE FT.Example: 10 x 10 = 100 Sq. Ft.
SQUARE FT. X DEPTH = CUBIC FT.Example: 100 x .5 (OR 6 INCHES) = 50 Cubic Ft.
CUBIC FT. DIVIDED BY 27 = CUBIC YARDSExample: 50 divided by 27 = 1.852 Cubic Yards
CUBIC YARDS X 1.35 = TONSExample: 1.852 Cubic Yards x 1.35 = 2.501 Tons
1.35 works for most aggregate. For dirt use 1.45 to convert to tons.
2.501 X 1.33 = 3.327 Tons
What we find here is that in a 10 by 10 area, going 6 inches deep we would need 3.327 ton of aggregate after compaction.
River Rock / Decorative Rock
1" Rock Coverage Per Ton
- 1" deep would cover 190 Sq. Ft.
- 2" deep would cover 95 Sq. Ft
- 3" deep would cover 45 Sq. Ft.
1 1/2" Rock Coverage Per Ton
- 1 1/2" deep would cover 120 Sq. Ft.
- 2" deep would cover 80 Sq. Ft
- 3" deep would cover 50 Sq. Ft.
2" Rock Coverage Per Ton
- 2" deep would cover 70 Sq. Ft.
- 2 1/2" deep would cover 50 Sq. Ft
- 3" deep would cover 35 Sq. Ft.
Fieldstone, Boulders and Rip Rap
4" - 8" Rock would yeild 110 - 150 stone
In a wall you would get 27 to 37 facial foot
8" - 1' rock would yeild 80 - 100 stone
In a wall you would get 12 to 15 facial foot
1' - 2' Rock would yeild 16 to 25 stone
In a wall you would get 8 to 10 facial foot
2' -3' Rock would yeild 3 to 5 stone
In a wall you would get 5 to 7 facial foot
Facial foot = Length x Height
Flagstone
3/4" to 1 3/4" will cover 110 - 150 Square Ft.
1 1/2 " to 2 1/2" will cover 80 - 100 Square Ft.
2 1/2" to 3" will cover 60 - 90 Square Ft.
Most flagstones will weight the same or close. In some cases you will need to consider the material used. (For example Slate)
Pavers
In finding the square footage of paver you would need to use the proper formula given above
Retaining walls and free standing walls
In finding the square footage of retaububg waks or free standing walls you would need to use the proper formula given above
Pond and Stream
Calculating Liner Size:
- Pond
- 2 X Pond depth + maximium pond length + 1 foot extra = Liner length
- 2 X Pond depth + maximium pond width + 1 foot extra = Liner width
- Stream
- Maximium length + 5 foot for every 15' of stream
- Example: 30' stream 40' liner
- Liner width for stream = maximium width + 3 = liner width
- Note: liner comes in 10', 15', 20', 25', ect.
Rock Calculation for Ponds:
Pond Size |
Sq. Ft. |
Rock and Gravel, Tons |
11' x 11' |
121 |
3/4" - 2" = 1 ton |
11' x 16' |
176 |
3/4" - 2" = 1 1/2 ton |
16' x 16' |
256 |
3/4" - 2" = 2 ton |
16' x 20' |
320 |
3/4" - 2" = 2 1/2 ton |
16' x 26' |
416 |
3/4" - 2" = 3 1/2 to 4 ton |
20 x 26 |
520 |
3/4" - 2" = 4 1/2 to 5 ton |
Rock Calculation for Streams:
For every 5' of stream | Rock and Gravel, Tons |
3/4" - 2" = 1/4 ton 6"-12" = 1/4 ton 12" - 18" = 1/4 ton 18" - 24" = 1 rock |
Note: Tonage on rock can be set to the look you are want in your pond or stream.