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How to Read a Tape Measure 

Using a Tape Measure or Rule  

I realize that some things learned in school are forgotten on the way home. Fractions is an area many of us choose to forget. Unfortunately, reading a tape measure or wooden rule is based on fractions. So, just in case, I figured it might be a good idea to go over it.

In the above photo you will see that the smallest increment of measurement on it is 1/16". (also the shortest line). On these measuring devices, 1/16" is the smallest increment. This is the fraction the inch is broken down into. Each line on the rule is an increment of that. The next line is 1/8". (or 2/16"). The third line, also a short one is 3/16". The length of the lines help to quickly determine if it's read as a multiple of a sixteenth, or an eight, or a quarter, and finally a half.

This method of line length makes it easy to find, say 9/16". Knowing that a half inch is equal to 8/16", it's a matter of going to the next sixteenth increment. I can't tell you how many times over the years, someone called out a measurement to me as, 1/2" plus one little line.

Also note the "hook" on the end of this particular rule. (It folds in to be flush with the edge of the rule). This is to allow easy measuring from the outside of an object. I rarely use it, but it's worth noting.

Prior to the invent of a tape measure, everything was measured with a wood rule. Generally, they were six feet long, with folding joints. These are still used, but not nearly to the extent they once were. Some are trade specific. For example the rules used by a brick layer would be of little use by a carpenter.

 Now days everyone has a tape measure, or several, each being used for a specific task. They are very convenient, come in all different lengths and thicknesses, and clip to your pocket or belt. 

It seems as though there's some sort of contest going on to see who can make the longest one. (size matters ?). I find a twenty five foot tape, that isn't extra wide to be most practical for all around convenience. (for my taste the max tapes are too wide to hold comfortably, however, being able to extend the tape without it collasping is pretty handy).

In my cabinet shop, I prefer to use a sixteen foot one. Cabinet making rarely requires a tape measure longer than that,yet, they're still large enough to keep track of, and have numbers large enough to see. We use a tape about eighty five percent of the time, but they do have their drawbacks.

For example, after a while, the metal end, which is designed to move the thickness of the metal itself, tends to move a little too much after seeing some use. The purpose of the movement is to permit measuring the inside of an opening, while pushing it tight to one side of the opening, and then measuring a part for it,  by hooking the end to a board can result in a sloppy fit.

I tend to hold the metal end of the tape with my thumb, and pull it tight, when taking an inside measurement. (at least when I can reach that far). This is rarely a problem for rough carpentry, since the measurements aren't as critical, as they would be in a cabinet shop.

The other option would be to use a rule. These too, are available in various configurations. Some are called inside read rules, (the rule on the bottom in the photo), meaning they are designed to lay flat on the item to be measured, with the numbers facing up, and the unfolded body of the rule also above the measuring area. The rule on the top in the photo is considered an outside reading rule, and is most common.          

Notice the metal extensions in one end. This permits the accurate measuring of insides of openings.