The ability to calculate the size of an area is a vital skill every groundskeeper should have. Square footage is a necessary piece of information for figuring rates of irrigation, chemical and fertilizer applications and seeding. How about estimating the number of bedding plants or bulbs you'll need for a bed? Or ordering sod? Or mulch? You can't perform these and many other tasks properly without calculating the area. Fortunately, the math you need to know is fairly simple. Here are some common shapes and the formulas you use to find their area.
Square or rectangle Area = L x W L = length W = width A = 90 ft x 50 ft = 4,500 sq ft
Ovals or egg shapes (within 5 percent accuracy) Area = 0.8 L x W L = length W = width at midpoint Area = 0.8 x 60 x 40 ft = 1,920 sq ft
Circle (within 5 percent accuracy) Area = 0.8 D2 D = diameter Area = 0.8 x 50 ft x 50 ft = 2,000 sq ft
Unusual shapes Divide the area into sections of regular geometric shapes, calculate the area of each section, then total:
Area of triangle + Area of rectangle + Area of one-half of circle = Total area
Irregular shapes Find the length of the longest line across the area. Every 10 ft along the length line, measure the width of the area at right angles to the length line. Total all widths and multiply by 10.
Area = (A + B + C, etc.) x 10 = (32 ft + 50 ft + 45 ft + 17 ft) x 10 = 144 x 10 = 1,440 sq ft
Triangle Area = 0.5 x B x H B = base H = height Area = 0.5 x 125 ft x 75 ft = 4,687 sq ft
Trapezoid Area = 0.5 x (A + B) x H A = one parallel side B = second parallel side H = height perpendicular to parallel sides Area = 0.5 (50 ft + 70 ft) x 30 ft = 0.5 x 120 ft x 30 ft = 1,800 sq ft
Circle Area = pr2 p = 3.14 R = radius Area = 3.14 x (30 ft x 30 ft) = 2,826 sq ft
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