LINEAR MEASURING
Linear – A measure of length
Carpenters are constantly taking linear measurements. They read measurements written on blueprints and
they use tape measures to layout and cut materials to length. Cabinetmakers measure spaces in which
cabinets are to be installed. Estimators take measurements off of blueprints and calculate material and labor
costs.
In the United States the Imperial system, which expresses linear distances in feet and inches is still widely
used. Much of the rest of the world uses the metric system. If you visit a construction site in Canada you
will likely see the carpenters carrying metric tape measures.
The metric system is actually quite easy to learn and use because there are no conversions. Conversely, the
Imperial system, using feet, inches and fractions of an inch, requires conversions in order to carry out
calculations. For example in the metric system if you wanted to add 793 mm (millimeters) to 620 mm it’s a
simple addition problem. 793 + 620 = 1413 mm. You can probably do that without pencil and paper.
The same measurements in the Imperial system would be approximately - 2 7 1/4 + 2 4 15/16. Add that
up in your head! The answer is 5 0 3/13. Methods for solving these types of problems may be found in
the next chapter.
The Imperial System of Measuring
Let’s talk about the Imperial system of measure a little more since we are stuck with it. Most of us have a
pretty good idea of what one-foot looks like. The paper on which these words are written is one half inch
shy of being one foot in height. A foot is further broken down into smaller units called inches. We all
know there are twelve inches in one foot.
Inches are broken down into smaller increments, which we express as fractions - one half -inch, one eighthinch, etc. Take a look at your tape measure and count how many divisions there are in one inch. Did you
count sixteen? If you used the first inch on the tape it may have been broken down into 32 divisions or
thirty seconds of an inch.
I once worked with a carpenter who had trouble reading sixteenths on his tape measure and he would call
out a measurement like this - twelve feet, three inches and one little one past a big one. Hopefully we can
improve on his system.
For now, let’s concentrate on the blown up inch illustrated below. Each space between the lines or hash
marks is one sixteenth of one inch because there are sixteen spaces. When a fraction of an inch is
expressed it should be reduced to its lowest common denominator. For example 8/16 is expressed as 1/2
and 4/16 is expressed as 1/4. Notice the sixteen lines in one inch are of different lengths. This is designed
to make it easier for you to find and reduce the fractions.
There are five lengths:
1
4
2
3
5
1 – Whole inch
2 - Half inch
3 - Quarter inch
4 - Eight inch
5 - Sixteenth inch
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Look at one inch on your tape and answer the following questions.
1. How many whole inch lines are there in one inch? ____ (There can only be one per inch)
2. How many 1/2 inch lines are there per inch?
____
3. How many 1/4 inch lines are there per inch?
____
4. How many 1/8-inch lines are there per inch?
____
5. How many 1/16-inch lines are there per inch?
____
The sum of your answers should total 16, the number of sixteenths per inch.
Sixteenths are normally the smallest unit carpenters use. Smaller divisions such as thirty-seconds or sixtyfourths could be used, but in most cases they are not practical. There are exceptions however.
In cabinetmaking and finish working, carpenters use thirty-seconds but in an unusual and very practical
way. If a measurement of 3 3/32 were taken, it would be written down or called out as 3 1/16+.
Explanation: One-sixteenth equal’s 2/32 and the plus sign indicates one additional thirty-second. A little
more sophisticated than one little one past a big one.
With practice you will be able to quickly measure any length. To help shorten the learning curve remember
that 1/2 is 8/16 so the hash mark before the one half inch mark is 7/16 and one past it is 9/16. Three
quarters of an inch is 12/16 so the hash mark before it is 11/16 and the one after is 13/16.
On the illustration below, write the appropriate fractions in sixteenths i.e. 1/16, 2/16, 3/16 above the
hash marks. Write them again under the hash marks in their reduced form i.e. 1/16, 1/8, 3/16
Practice using you tape measure by marking the following measurements on any piece of material at least
two feet in length:
6. 1-3 1/4
7. 1-8 3/8
8. 0-7-3/4
9. 0-4 1/2
10. 1-5 7/8
11.
12.
13.
14.
15.
1-9 11/16
0-10 5/16+
1-2 5/8
0-11 15/16
1-1 7/16
16.
17.
18.
19.
20.
0-8 13/16+
1-6 7/16
0-09/16+
0-4 3/16
1-111/16
TAPE MEASURES
 Lengths – Tape measures come in a variety of lengths. One hundred footers, fifty footers,
thirty footers, twenty-five footers, twenty footers, sixteen footers, twelve footers and ten
footers.
 Blades – Most of the commonly used retractable tape measures have a Mylar blade that is
flexible but rigid in its length. The blades of some of the longer tapes are constructed of cloth
or steel.
 Units – Imperial (feet, inches and fractional inches), metric and engineering (the foot is
divided into 100 equal units) are most common.
 Retractability – Blades on standard tapes used by carpenters retract into the case
automatically. This is made possible by a coil spring. Most of the longer tapes, fifty footers
and better, are retracted by a hand crank.
Next, a few words about the myriad of tape measures available in the market today. The first thing you
should think about is the length. If you are a framer, twenty-five and thirty foot tapes are for you because,
framers often layout walls requiring longer tapes. On the other hand if you are a cabinetmaker you will
want a twenty-five footer for taking site measurements and a ten to twelve footer for building cabinets.
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A second consideration to make when purchasing a tape measure is what system of measure is wanted? A
cabinetmaker may want a tape with both Imperial and metric scales. Much of the latest hardware used in
cabinetmaking requires metric dimensioning. For the most part, a carpenter who is framing or doing finish
work will simply want an Imperial tape measure.
THINGS TO WATCH OUT FOR:
Look at the hook on the end of your tape. With a little help it should move slightly back and forth. That
movement is by design and should not be restricted. The reason it moves is to facilitate inside and outside
measurements.
An example of an inside measurement would be measuring between two walls. The outside edge of the
hook is butted against one wall and the measurement is taken at the other wall. When taking an outside
measurement the inside edge of the hook is placed over an object, pulled tight, and the measurement is
read on the other end of the tape.
In each case you are measuring on opposite sides of the hook. Because the hook has thickness it moves
back and forth to insure the measurement always starts at zero inches. I mention this because I encountered
a student in one of my classes who had wrapped duct tape around his tape measure where the hook
attaches. When I inquired as to the reason for the duct tape, he told me the hook was loose and he had taped
it down to increase the accuracy of his measurements. Good intentions don’t always have good results!
One additional point about the hook of your tape measure: Make sure that it remains straight, flat and
oriented ninety degrees to the Mylar blade. Often times when a tape is dropped it lands on the hook and
bends, affecting the tape’s accuracy. Look at the hook on your tape periodically to make sure it is straight.
If it is bent, place it on a flat surface and carefully flatten it out with a hammer.
Measure the lengths of the lines below and record the answers on top of the line. If necessary, round
up to the nearest sixteenth.
Example:
7/8
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
OTHER MEASURING DEVICES
There are other means of taking linear measurements besides the Mylar retractable tape measure. However,
to cover all of them is beyond the scope of this book.
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