Measuring Superficial Areas. Measurements are made across the widest and the narrowest parts of the plot, the two figures are added together and then divided by two. Two similar measurements are made across the greatest and least lengths of the plot and treated in the same manner. The average width and average length obtained by this means are multiplied together to give the approximate superficial area — in square feet if the measurements were in feet, in square yards if in yards, or in square metres if the measurements were in metres. Square feet can be reduced to square yards by dividing by nine. Conversely, square yards can be converted into square feet by multiplying by nine.
If the plot or bed is rectangular, only two measurements need be made, one for width and the other for length. These are then multiplied together.
To estimate the area of a circle, measure from the centre to the edge, multiply this by itself and the result by 34.
Estimating Bulk. Measurements of capacity or bulk are made in cubic feet, cubic yards, cubic centimetres or cubic metres. Three, instead of two, preliminary sets of measurements must be obtained — one for average length, one for average breadth, and one for average depth — but these are made in the manner just described. All three are then multiplied together, the answer being in cubic feet if the original measurements were in feet, cubic yards if in yards, cubic centimetres or cubic metres. Cubic feet can be reduced to cubic yards by dividing by twenty-seven.
Estimating Gravel. A ton of gravel contains from 19 to 20 cubic feet, but gravel is usually sold not by the ton but by the ‘yard’ (i.e., cubic yard). A thickness of from 2 to 3 inches of gravel is required for surfacing a path, and at this rate a ton of gravel will cover from 9 to 13 square yards, while a ‘yard’ of gravel will cover from 12 to 18 square yards.
Estimating Paving Slabs. Crazy pavement is proportionately heavier than gravel. A ton contains from 13 to 14 cubic feet, and the covering area depends upon the thickness. Usually ‘crazy’ is sold in two grades, ‘thin’ varying from to 14 inch in thickness, and ‘thick’ from 14 to 24 inches thick. The former has a covering capacity of from 14 to 16 square yards and the latter from 8 to 9 square yards per ton. Similar remarks apply to rectangular paving. York paving covers 10 to 11 square yards per ton.
Estimating Walling Stone. Walling stone is similar to crazy paving and its covering capacity depends upon its thickness. A usual measurement is 6 inches, and this has a covering capacity of about 3 to 4 square yards per ton.
Estimating Soil for Filling. Soil for filling up beds, etc., varies in bulk according to its texture and the amount of water that it contains. Sandy soils are the lightest and may reach
26 to 27 cubic feet to the ton, while heavy clay barely touches 18 cubic feet for the same weight. The average for good fibrous loam is about 23 to 24 cubic feet. Potting loam can be estimated at the same rate, while potting sand averages 24 cubic feet per ton. Leaf-mould is much lighter, though it will vary considerably according to its age. Often these materials are sold by the load instead of by the ton. The volume of a load is approximately
27 cubic feet (1 cubic yard).