CONVERSION OF UNITS
To convert a measure expressed in terms of
one unit to the equivalent in terms of a different
unit is, when you know the ratio between the
units, a simple proportional equation problem.
Suppose, for example, that you want to convert
a linear distance in engineer’s measure (feet and
decimals of feet) to the equivalent in carpenter’s
measure (feet and twelfths of feet) to the nearest
one-eighth in. Suppose that the original distance
is 12.65 ft. This means “12 ft and 65 hundredths
of a foot.” You want to determine first, then, how
many twelfths of a foot there are in 65 hundredths
of a foot. The original ratio is 12/100. The
proportional equation solution is as follows:
Therefore, there are 7.8 in. (twelfths of a foot)
in 0.65 ft. The next step is to determine how many
eighths of an in. there are in 0.8 in.; that is, in
eight-tenths of an in. The initial ratio is 8/10, and
the proportional equation solution is as follows:
Therefore, there are (rounded off) 6/8 in,, or
3/4 in., in 0.8 in. In 12.65 ft, then, there are
12 ft 7 3/4 in. to the nearest 1/8 in.
Actually, the proportional method used above
can be simplified by using the following solution:
Convert 12.65 ft to the nearest 1/8 in. in
carpenter’s measure.
12.65 ft = 12 ft + (0.65 x 12 = 7.8 in,)
– 12 ft 7.8 in.
—
= 12 ft 7.0 in. + (0.8 x 8 = 6.4
eighths)
= 12 ft 7.0 in. + 6/8 in. or 3/4 in.
to the nearest eighth in.
= 12 ft 7 3/4 in.
In converting from
linear measure, or vice
engineer’s to carpenter’s
versa, surveyors working
with values to only the nearest 0.01 ft fre-
quently use the following conversions to decimal
equivalents of inches from 1 through 11 and
decimal equivalents of the common carpenter’s-
measure subdivisions of the inch.
1 in. = 0.08 ft
2 in. = 0.17 ft
3 in. = 0.25 ft
4 in. = 0.33 ft
5 in. = 0.42 ft
6 in. = 0.50 ft
7 in. = 0.58 ft
8 in. = 0.67 ft
9 in. = 0.75 ft
10 in. = 0.83 ft
11 in, = 0.92 ft
1
– in. = 0.01 ft
8
Using these values, you can convert decimals
of a foot to inches carpenter’s measure, or inches
carpenter’s measure to decimals of a foot, very
easily. To convert (for example) 0.37 ft to inches
carpenter’s measure, you have the following:
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