How to Read a Ruler
So you're trying to build a woodworking masterpiece and the plans call for you to
cut a board to 4' 11-3/8". No problem….. Until you pick up the tape
measure and realize that there is no clear marking for 11-3/8"!!! Now you
need to understand how to read a ruler. It's actually a lot simpler than it
The first thing we need to clarify is the symbols used in most woodworking
plans. The symbol ' (apostrophe) represents feet. The " (quote) symbol
represents inches. So a plan calling for a board to be cut to 4' 11-3/8" is
asking for "four feet eleven and three eighths inches". Because this
can be confusing most plans will call out this measurement only in inches; in
this case 59-3/8" or "fifty nine and three eighths inches".
Now that we've covered the basics it's back to understanding all of those little
marks on the ruler. A standard tape measure (or ruler) in the United States is
divided up into feet and inches. Each foot is divided into 12 inches. The
problem starts with the subdivision of the inches. In each inch there are a
number of lines of different length. The longer the length of these lines, the
larger the unit of measurement.
For example. 1. The longest line in the inch is in the middle. This is the
half-inch mark and there is only one. 2. The next shortest line is the 1/4"
(one quarter of an inch) inch mark and there are only two of these. 3. The third
shortest line is the 1/8" (one eighth of an inch) mark and there are four
of these. 4. The fourth shortest is the 1/16" (one sixteenth of an inch)
mark and there are eight of these. 5. Some rulers will go a step further, down
to 1/32" but this is often more precise that most woodworking cuts need to
be. Click on Image to Enlarge
On the typical ruler the basic (smallest) unit of measurement is 1/16". If
you count the distance between two inch marks (one inch) you will find sixteen
lines. This is because an inch is 16/16th of an inch long. Because we like to
express fractional numbers in the largest unit possible we call it one inch. So
it follows that if you have 8 lines, or 8/16" you have a half-inch or
½". And likewise, if you have 4 little lines, or 4/16" you have a
quarter inch and so on.
At first it can be a little cumbersome to count these lines but over time you
will learn to recognize the lengths and the different units of measurements they
represent. This often starts with the ½" mark and progresses down the
line. Over time a measurements like 59-3/8" can be located quickly.
OTHER MEASUREMENTS You might have noticed that every 24" on the tape
measure are marked with a contrasting black background and every 16" is
marked with a red background. The marks are used by construction workers for
spacing wood studs in a wall or joists in a floor/roof. 16" spacing is used
most commonly for load bearing walls and 24" for non-load bearing walls.
The small black diamonds represent a less common spacing scheme. Click
on Image to Enlarge
Think you're up to the test? Check out this neat measurement quiz on
- You can also change the difficulty level of the quiz.