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You know how to read the big numbers on a measuring tape (or is it a tape measure?), but do you know everything the measuring tape does and what all the markings mean?
You’ve heard the adage, “measure twice, cut once…unless you forgot what the measurement was”. Well, pffftt, that’s a waste of time.
The principles I work under are barely measure once, cut 7 times, realize I’ve gone too far, break the piece over the workbench in rage-filled-anger, drive to the lumber store, get more wood, come home…and then measure twice, cut once.
But, that’s because I’m what’s known as a professional.
If you want to be a professional like me then I’m going to talk about the most ubiquitous tool in woodworking: The tape measure.
We’ll talk about its markings and then we’ll dive in to some of its basic functions and some less well known tricks.
The Parts and Markings
The guts of a measuring tape consist of the blade wound up around a spring. The blade can be made of steel and coated in lacquer or nylon, it can be stainless steel, or it can be made of fiberglass. Then, there’s the mechanism that holds it in place by putting pressure down on the tape, itself.
They come in all different sizes. I recommend using a shorter 9 ft tape for woodworking. You will hardly ever need more than this length for most woodworking projects and the smaller form factor is nicer to work with. The only drawback to the smaller tape is that it’s so narrow that the hook makes it hard to read the marks on the first 1/2″. For larger carpentry jobs I use a 16 ft tape.
I have tapes that have a metal clip for hooking on your tool belt or apron and with flat steel on the other side so that I can hang it on a magnet. Some tapes have magnets on the end of the hook to help keep it in place and you can pick up stuff you’ve dropped.
I just mentioned the hook, which is this part at the end of the tape. It functions as a stop to keep the tape from rolling up inside the body, it acts as a stop on the edge of whatever you’re measuring and lets you extend the tape, and it can also do a couple of other things that we’ll talk about a little later.
You’ll notice that the hook on your tape moves back and forth. It’s setup to move the thickness of the hook itself. This is for inside and outside measurements. If I need to measure between two things, or if I can’t hook onto an edge because of a board or bevel, the hook collapses in the thickness of itself, so that the measurement will be accurate. For an outside measurement the hook extends and the tape is setup to account for that distance.
Everyone knows that the numbers indicate the length in whatever unit of measurement the tape is in. Sometimes a tape will have imperial measurements on top and metric on bottom.
If it doesn’t have two units of measurement, the hashes might be the same, but it will have smaller increments labeled on bottom to make it a little quicker and easier to read the hashes. Other tapes will have hashes for every 1/8″ on top and every 1/16″ on bottom.
The length of the tape could be printed towards the end of the blade right next to the hook. I assume this is so that the user won’t have to rely on the length being printed on a sticker on the case which can easily get worn off over time.
There will be some marking every foot or decimeter, depending on the unit of measurement. That length will usually be red, and/or have an arrow to make it stand out.
Beyond the first foot secondary markings are added to help you quickly calculate the feet and inches. So 1 ft 4 inches, for example.
Every 16″ will also stand out in some way to indicate the length between wall studs if the wall is built to the 8 ft standard.
The length of the body or case is usually printed on the back. This is used for inside measurements and we’ll talk about that a little later.
At every 19 3/16″ there is a little black diamond. These are for measuring 5 equal parts in an 8ft sheet of plywood for engineered I beam joists used to frame a floor. This is an esoteric feature you will likely never need.
Less commonly, your tape may have markings on the back side of the tape. I’m not exactly sure of every use the manufacturers intend for this feature, but I know that electricians use it to easily mark measurements on conduit. There is a little tab stop on the front and then the concave nature of the tape and vertical layout of the numbers make it perfect for marking pipe.
Speaking of the concave nature of the blade, it is shaped like this to allow it to stay straight as you extend it. The amount of distance it will extend without breaking is called the “standout”.
What Can the Measuring Tape Do?
Now, let’s talk about some things you can do with the tape.
The hook of your tape may have a slot in it. And while this is weight reduction to make it high speed, low drag…kidding….it’s really to hook on a nail or screw.
You won’t use this in woodworking too much but if you ever need to measure from something that isn’t going to be a finished surface, like say wall studs, you can pound in a nail or drive a screw, hook your tape on, and measure for the next one.
Some hooks are serrated, but you can do this next trick even if it’s not.
The measuring tape can act as a scribe tool in a pinch. If you need to measure 12″ out from a spot, hold the tape at 12″ and then use the hook to make a mark. It works much better if it’s serrated, but a smooth hook will still make a scratch.
Measuring between two surfaces can be a bit tricky. We tend to bend the tape to try and estimate the distance. And while eyeballing and estimating measurements is a perfectly valid way to build accurate projects, let me show you two ways that are even better.
The first is to use the width of the case printed on the back. Extend the tape and push the hook up against one end and then push the case up against the other end. Add the case width to the measurement showing on the tape.
The second method involves measuring from one end to about 10″ and then flipping the tape around and measuring from the other end to that 10″ mark.
To find the center of a board, especially when it’s a weird fractional width, pivot the tape until a whole number is on the edge. Mark the halfway point of that measurement and that’s your center.
You can also use this to mark equal intervals along the width of the board.
This next method is an easy way to subtract a measurement from another measurement. (Notice these last couple of tips aren’t necessary if you’re using metric. We Americans apparently like to challenge ourselves). If I wanted to subtract 5 3/8″ from 32 1/16″ I fold the tape back and put the hook on 32 1/16″. I need to make sure the hook is collapsed and the hashes all line up and then look at the measurement that 5 3/8 intersects with. This measurement comes out to 26 11/16″
To check a 4 cornered project for square you can measure from opposite corners and they should be exactly the same measurement if all 4 corners are 90 degrees.
You can also check one corner for square with a consistent ratio. I use 3, 4, and 5. I measure 3″ up one side from the corner and 4″ up the other side. Those two marks should be exactly 5″ apart if the corner is 90 degrees.
Here’s a simple way to test that your tape measure is accurate. Measure from the edge of a workpiece and make a mark at say 1″. Then slide the tape over until 1″ on the tape is lined up with the edge. If your mark doesn’t line up with the 2″ line on the tape then it isn’t accurate.
Along those same lines you can check inside and outside measurements by sliding a board up to the edge and pushing the tape up to it. The 1″ line on the tape should line up with your mark.
Usually inaccuracy is due to a bent hook and it’s easy to straighten out. If also could be the movement in the hook which is harder to fix correctly.
The next two tricks allow you to draw a straight, measured line and a circle.
Hold the tape on the edge to some measurement. In this case I want to measure 10″ from the edge along this workpiece. Hold it in place and place your pencil at the end of the hook and slide it down the edge.
To make a circle, drive a screw or nail in the middle of where the circle should be, hook the slot onto the head of the screw, and hold your pencil at the measurement of the radius. If I want a circle 10″ across, I’ll hold the pencil at 5″ and swing the tape around.
Let me know in the comments of the video above if you knew all of these or know of something I missed!
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