How to Interpret Blueprints:
Reading an Architect’s Scale &
Understanding the Alphabet of Lines
Interior Design II: Objective 5.02
What is an Architect’s scale?
• A triangular shaped instrument used
for making or measuring scaled
drawings such as blueprints or floor
plans.
What is an Architect’s scale?
• The scale can be read from left to
right and right to left.
• 1/8” scale would be read from left to
right and the ¼” scale would be
read from right to left.
The left side begins with 1/8" scale ….
1/8
0
4
46
8
44
12
42
40
38
… and the right side begins with 1/4" scale
80
8
84
6
88
4
1/4
92
2
0
The left side begins with 1/8" scale ….
1/8
0
4
46
8
44
12
42
40
38
Look at the 1/8” scale and read from left to right.
The upper numbers
… andrepresent
the right side feet.
begins with 1/4" scale
80
8
84
6
88
4
1/4
92
2
0
The left side begins with 1/8" scale ….
1/8
0
4
46
8
44
12
42
40
38
1/4”
scale,
read
from right
left following
lower
LookAtat
the
1/4”
scale
andtoread
from the
right
to left.
numbers
The lower numbers
… andrepresent
the right sidefeet.
begins with 1/4" scale
80
8
84
6
88
4
1/4
92
2
0
What does “drawn to scale” mean?
• On a scaled drawing, a small
measurement is used to represent
a large measurement.
• For example, one-fourth inch (¼”)
on the plan may represent one foot
(1’) in the real world.
What does “drawn to scale” mean?
• Floor plans for residential structures
are usually drawn at ¼” = 1’.
• Commercial buildings may be
drawn at 1/8” = 1’ if they are too
large to fit on the desired sheet size
at ¼” = 1’.
Step 1
Determine the drawing scale.
Step 1
Determine the drawing scale.
Step 1
Determine the drawing scale.
Step 2
Find the matching number on the architect’s scale.
Step 3
Place the scale on the print. Place the mark above the
zero at the beginning of the line to be measured.
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Step 4
Use the scale to draw
• To draw your own prints, determine the
length of the object to be drawn, then
scale it down accordingly using the
architect’s scale.
• For example, using the 1/4”= 1’ example, a
wall 20 feet in length would become 20/4
or 5 inches on the blueprint.
Example:
The Length of a Work Table
Find the “0”
point on the ¼
scale …
Align it with the
left corner of the
table top
80
8
84
6
88
4
1/4
92
2
0
Example:
The Length of a Work Table
Plan View
80
8
84
6
88
4
1/4
92
2
0
Looking from
Right to Left
along the scale,
note that the
table is “6” units
or 6 feet long.
0
2
92
4
88
The table is
somewhere
between 2 ½
and 3 feet high
…Can we be
more precise?
1/4
Example: Now measuring the height of the table
2
92
4
88
Slide the
scale down
so that the
nearest
whole foot
measure
(2’) is
aligned
with the
bottom of
the table.
0
1/4
Example: Worktable Height
1/4
Example: Worktable Height
2
4
2’
92
0
9”
88
Then read the
area “above” the
“0” … a distance
of about 9” … so
the table would
be 2’ plus 9” high,
or 33”
Now it is your turn!