M2
meters. The rule of 3's can help, and
Dual dimensions are a complete waste
is fairly accurate.
of time in construction documents.
When english units are there,
Feet times three, move decimal left one
readers use them and ignore the
digit.
metric.
50 feet, times 3 = 150, move decimal,
Use preferred scales:
15 m
1:1 1:2 1:5 1:10 1:20 1:50 1:100
20 feet x 3 = 60, yields 6 m
1:200 1:500 1:1000
Rule of 4's For Hectares This rule can
Many state DOTs use 1:250 for urban
help develop a general feel for
plan sheets.
converting commonly used acres to
hectares (ha), or hecters, as many
ISO Paper Sizes are the standard
pronounce it.
international paper sizes, and are
often available within a few weeks,
Multiply acres times 4, move decimal
anywhere in our country, from
left one digit.
domestic sources.
30 acres x 4 = 120. Move decimal yields
Many state and federal agencies,
12 hectares.
such as Army Corps, Huntsville
10 acres x 4 = 40, yields 4 ha.
Division, are now using them.
Rule of 10's For Square Meters
We are now generating designs in
this region around A1 size. Designs
Square Feet divided by 10 = Square
are to now use ISO sizes, see below.
Meters
The Government Printing Office now
stocks A4 paper for purchase by
500,000 SF divided by 10 = 50,000 m2
other agencies.
For diehard fans of the old system, who
can not bring themselves to use meters,
Many state highway groups have
the ideal transition unit may be the
adopted A1 as their standard drawing
metric foot, equal to 300 mm, or 0.3 m.
size.
So the 8 foot ditch becomes 8 metric
A0
1189 x 841
feet, or 2.4 m.
A3
420 x 297
A1
841 x 594
Drawings
A4
210 x 297
A2
594 x 420
Good drawing practice is demonstrated
on the sample drawings in this
Specifications
document.
Several questioned our use of mm for
Centimeters shall not to be used.
large dimensions. In response, we
have utilized both m and mm in
Dual dimensions shall not be used.
specifications in the interim
Example, 200 mm (7-7/8")
period, and have found little
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