Tape Measure Test: How to Read Markings on a Tape Measure, Including the Black Diamond
MulWark Digital Tape Measure Review


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Ever find yourself wondering: What is a tape measure test?

If so, you’ve come to the right place. A tape measure test consists of a series of questions around this measurement tool. These questions include: how to accurately read the measurement results, if they are easy to read, what the various tape measure markings stand for, and ways to use the tool to achieve accurate measurements.  Like any test, it’s easy if you take some time to prepare and familiarize yourself with the material.

Whether you are preparing for a tape measure test for employment qualifications, or just want to know how you can better understand how to read a tape measure, we are here to help. This article will cover everything you need to know in order to grasp the art of reading inches & feet (imperial measurements), as well as centimeters, millimeters & meters (metric measurements). In addition to the numerical units, we’ll cover the meaning of the small diamond shapes and what the red numbers mean when measuring with your tape blade.

Fast fact: “blade” is another name for the tape itself – which can be made of various materials such as nylon coated steel tape, lacquer coated steel tape, & tape with a mylar polyester film, to name a few).

Let’s get started!

Tape Measure Markings

Ever wonder what all the various length markings on a measuring tape are for?

Firstly, let’s cover the most common markings found on a foot tape measure. Generally speaking, people use building and/or carpentry tape measures. These are just your average, run-of-the-mill measurement variety. On these tapes, you will see several black lines running perpendicular to the edge of the tape in-between each of the feet and inch markings. These black lines are of different lengths, helping the user differentiate between the various measuring units provided on the tape.

Of these black lines between inches, the longest indicates the halfway point between each inch mark. These are often referred to as “half-inch marks”. For example: If you were instructed to measure and cut a piece of wood 4 ½ inches in length, you’d make a pencil mark on that piece of wood at the longest black line, found exactly in between the 4 and 5-inch markings (known as the half inch mark) on the tape measure.

Next up? The “quarter-inch markings” are the next longest lines on the edge of the tape. Hence, these markings divide every 1 inch marking into four equal parts, each part equivalent to one-quarter of an inch long.

This same pattern is true for the next two smaller black line markings on the tape measure within the quarter inch. Going one size of the black line down from the quarter-inch marking, you’ll find the “one-eighth marking”. The last, and smallest of the black lines (on each side of the 1/8th inch marking, is the “one-sixteenth marking”. Reading a ruler works the same way as tape measure reading.

On the metric side of your tape measure (if it shows both), it’s more straightforward as the metric centimeter is divided by 10 millimeters, with only the half-centimeter line marked by a long black line.  I know that sounds easy by comparison, and so lives on the never-ending debate about the imperial vs metric systems. Not something we’re going to try and solve here!

That covers the numerical markings for both the metric and imperial versions of this common measuring tool, but there’s still more!

Quick tip: Each time you measure anything, measure twice and cut once! You can always measure something again and again, but once the cut is made, there’s no going back.

Black Diamond on Measuring Tape

Here’s the part where you go from a novice user to an expert that really understands the full potential of a tape measure.  We’ll start by explaining what the small black diamonds on a tape measure represent. This will save you a lot of time, especially when working in homes for regular handyman tasks, or full on major house builds / remodels.

The first of the small black diamonds you’ll find on a measuring tape is at the 19.2” mark. The next of the diamond shapes is found at 38.4”, then the 57.6”, 76.8”, and 96” (or, the 8 feet point – also known as the “8-foot rule”). These black diamonds represent the center point of the studs along a wall (when placed according to code), and these markings enable 5 studs per 8 feet, all evenly spaced – common for a wall in your home. So instead of getting out a stud finder to locate each stud, simply use the small black diamonds on your tape measure. Some tape measures also use red markings for every 16 inches along a tape measure. This is done because 16” is also a common distance for studs or joists, and a 16” allows for a 6th stud per 8 feet, again all evenly spaced..

Studs, and most traditional floor joists, are placed either 16 or 19.2 inches on center. That means you’d have to install floor trusses at the 19.2” centers in order to place them correctly and have standard truss layouts. That is exactly what the black diamond marks, otherwise known as ‘truss marks’ are for.

Tension or Temperature Markings

Have you noticed that tape measures have ’20°C’ and ’50N’ markings near the blade’s tip? This has to do with the accuracy of the tape measure.

The EC Accuracy levels (Class 1 or Class 2) say that a tape’s blade is true to that specific standard at 20°C temperature and 50N drawing force (N meaning Newtons). The temperature in the laboratory where the blade’s precision is evaluated is 20°C.

It’s difficult to guarantee the tape measure’s accuracy if used at temperatures other than the standard 20°C or with a pulling force greater than or less than 50N. While this does not necessarily imply that the tape’s accuracy has been compromised, you may have to adjust for the temperature or force change manually.

Roman Numeral System for Accuracy

On taking the blade out of the case, you’ll discover a Roman numeral printed in black or red inside either a rectangle or a circle. These indicate the various measurements, with I indicating the most accurate and III indicating the least accurate.

There are 4 widely accepted accuracy levels in tape measurement. The most accurate is Class 1 (represented by the Roman numeral ‘I’). Class 2 (designated by the letter ‘II’) is the runner-up in terms of accuracy, and Class 3 (III) is the third level and least accurate of the batch.

The blades of unclassified tapes won’t have these markings. Unclassified describes the measuring tapes that have not been evaluated and are not guaranteed to meet a certain degree of accuracy.

Class 1 tapes are gaining popularity, particularly amongst those who demand the best precision. However, most of today’s tape measures are EC Class II accurate. With that said, class II tapes are more than enough for an average person’s needs, given that they use them correctly.

How to Easily Read a Tape Measure

Are you preparing to take a tape measure test or are you just wanting to know the best one to read one for your DIY project? Below we’ll go over the easiest and fastest technique to read a tape measure using all of these lines.

The standard tape measure marks begin at 16 lines and go up to 1/32nd of an inch. Understanding the marks is the first step to reading a tape measure. Starting from the longest to the shortest, the line marking will include:

  • The total number measurement found in 1 inch, 2 inch, and 3-inch intervals
  • The half-inch
  • The quarters of an inch (1/4 or 3/4)
  • The eighths of an inch (1/8, 3/8, 5/8, or 7/8)
  • The sixteenth of an inch (1/16, 3/16,5/16,7/16,9/16,11/16,13/16,15/16)

When writing down your findings, remember that 15″ refers to inches, while 15′ refers to feet.

Types of Tape Measures

The easy-to-read tape measure is a type of tape with a label for a complete inch and eights and quarters of the inch. These are labeled 1/8, 1/4, and 3/8 and will make reading the tape measure easier.

Another type is the basic tape measure, with multiple numbers and varied line sizes. This can be more complicated than the easy-to-read tape measure and may take awhile to get used to it and how it functions.

Tape Measure Test for Employment

As previously mentioned, depending on the job you are applying for, you may be asked to complete a tape measure test prior to employment.

Tape measure tests usually consist of questions aimed to determine your level of experience with a tape measure, and the knowledge you have around measuring tools in general. You may be asked questions such as, “How many marks can be found in the spacing between each 1-inch mark on a measuring tape?” (answer is 15 marking lines between each inch) or, you may be given a series of tape measure images and asked what each line on the tape represents (as we covered already above). A handful of tests may also inquire regarding the more specific markings on a measuring tape, such as the black diamond mark.  Beyond the most important part that we’ve covered above with regard to measurements, there are other features to familiarize yourself with on the typical tape measure. Let’s look at those now.

Tape Measure Mechanics

Beyond the blade itself with the measurement features, there are some important features of a good tape measure.

Most tape measures worth their salt have a locking mechanism. This is typically above where the blade exits the mechanism, and by engaging the locking mechanism it prevents the tape measure from winding back up. This piece of the tool comes in especially handy when working alone and you want the tape to stay extended while you make markings or align various measurements.  It’s great for those times when you need to measure several items to the same length.

Another common feature for the hardier tape measures is a belt clip. This is on the backside of the measurement tool, and makes it easy to keep your tape measure handy by attaching the belt clip to your belt, top of pants, pocket, or tool belt. Getting in the habit of keeping your tape measure on your person, and in the same spot, will save you loads of time in trying to track down where you may have left it otherwise. Be smart & be efficient by being consistent in where you keep your tape measure when not in your hands.

And finally, while less popular, there are magnetic tape measure options. These are a bit gimmicky to me, and something that most experts find gets in the way of accurate measurements, and quick and effective use of the tool.  But there are certainly use cases where a magnetic tape measure is desirable, but this isn’t something we’d recommend seeking out for a traditional tape measurement device.

Not to be too partial, but since you’re still here… we thought you might appreciate a recommendation. The Stanley brand is one that’s earned its stripes over the years, and in particular the Stanley Fatmax is a model well known by those who know a good tape measure. The Fatmax tape measure has the above features, but also the durability and ruggedness you want in a tool that’s needed to be reliable and available on a moment’s notice. If you don’t need something as tough as the Fatmax, Stanley Tools also manufactures the powerlock tape measure, which is a great measuring tool for common use, and comes in sizes small enough to be considered pocket tape measures. Both of the above have options with metric units.

The Stanley Powerlock is a great first tape measure, but once you’ve become a real handyman or have aspirations to do more (or have worn out your first powerlock), then it’s time to consider graduating to the Stanley Fatmax.  It may just be the last tape measure you every need to buy.


This is a great place to spend some time familiarizing yourself with both the metric and imperial ways to measure lengths, and should prepare you well for any tape measure test. For employment or doing work on your own home, you should take the time to know your measurement tools so you can be safe, accurate, and deliver quality work.

That said, if you came here to better your understanding of where to find the best measuring tape tool, you should check out our review of the best selling Amazon tape measures for 2020!

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