Picture of How to Read a Ruler (and other simple tricks).
While it may seem to be a very basic skill, being able to read a ruler is the foundation to just about any project you make by hand or even with a Shopbot!  Reading a metric ruler is pretty simple- no fractions, everything converts nicely in factors of 10, and its pretty straight forward.  The English system, however, can be kind of confusing- fractions, units, and symbols.  This instructable will help you understand how to use a "standard" ruler better; specifically being able to read fractions of an inch or "Drawing the Inch" as I call it with my students.

The cool thing about knowing how to label the fractions inside of an inch is that you can use it as a calculator to reduce fractions!  Follow along and I'll show you how.  This instructable may be a little hard to follow if you don't read it through all the way to the end before trying it out.

Step 1: Start your Inches!

Picture of Start your Inches!
Gather supplies.  See Picture 1. You need:

Pencil or Pen

That's it!

A few definitions that might help you understand this instructable a little better:

Numerator:  The number above the line in a common fraction
Denominator:  The number below the line in a common fraction

The easiest way I have found to explain an inch is to draw it out, starting with a mark representing zero and a mark representing 1.  These DO NOT HAVE TO BE ACCURATE!!!  I find it is a lot easier if you make your "inch" BIG to give you more room to write in the fractions.  SO:

On the paper, Draw a rectangle as shown in Picture 2 and 3.  This is going to be our "ruler".  Remember to make it big!  On the ruler, make a mark, also as shown in Pictures 2, 3, and 4.  This will be out 1 inch mark.
Virginia20123 months ago


Here's my little piece of the world...


LaurieL311 months ago

Wow! How cool is this. Every everybody should know this little trick. This has taught me how to read a ruler and I do not think I will forget it. Thank you soooo much for sharing this.

dorkpunch (author)  LaurieL311 months ago

Thanks! Glad it could help. I've wondered who views this instructable- There are hardly any comments yet it has over 100k views. Would love to hear how (if?) others are using this in some way?

tholopotami2 years ago
A nice instructable! Some times one needs to discuss the obvious. I am a physicist, I live in a metric world and during my education I had to use the log rule a lot. The way I see it the metric system is more "flat" since 0.7 has no qualitative difference than 0.8 and it is easier to think of the increase, on the other hand when you jump from 1/4 to 3/8 you have to re-adjust your mind in dividing the pie in 8 instead of 4 pieces. Not to mention that if you ask me where the 13/16 is on the ruler I'll have to think a little.
k24tea3 years ago
This is a great way to explain and use fractional measurements in any project, or to learn and practice fractions for any other purpose. Kudos for your teaching method! (I agree, metric is a LOT easier, but sometimes you just have to work with what you've got.) Next, maybe somebody can show how to use those 3-sided architectural scale rulers ...
EmcySquare3 years ago
..Still don't get the reason why one should choose to hurt himself so much...

Why not simply jump to the metric ???
dorkpunch (author)  EmcySquare3 years ago
I agree... The metric system is just so much easier. Unfortunately, my students still need to know BOTH systems. Guess which one they struggle with more? I will say this though, my students understand their fractions a lot better after learning their inch.