Tape measure with small black diamond circled and a question mark present.

What does the Diamond on a Tape Measure Mean? (Answer Simplified!)

Tape measures are one of the most important tools on the jobsite. Whether you work in construction, or do home projects on the weekends, a tape measure is key.

They can be challenging to read if you do not have much experience using one. For most brands you will often see a black DIAMOND mark located at specific points. If you are wondering what that diamond means, you are in the right place.

I will give you and in depth explanation of what that diamond means and is used for. We will also discuss another common marking found on tape measures.

Of note, depending on the brand it may not be a diamond. I have also seen circles used.

What does the diamond on a tape measure mean

The diamond found on most tape measures is found every 19.2 inches. It’s the marking most commonly used for spacing flooring “I” joists and trusses of roofs. You will find the black diamonds located at: 19.2 inches, 38.4 inches, 57.6 inches, 76.8 inches, and 8 feet.

Black diamond found at 19.2 inches on Stanley tape measure.

Black diamonds

The black diamonds on your tape measure are used as a marker. It is most commonly used for quick and easy placement of “I” shaped flooring joists and or trusses of roofs. These are commonly known as “engineered trusses.” There are many benefits to using engineered trusses these days.

I shaped joists commonly used for floor joists and trusses used for roofs.
I shaped Joists and engineered trusses for roofs

When using this symbol, you want to make sure the diamond is placed directly in the center of the material. This is commonly referred to as diamond on center.

Diamond on tape measure placed at center of piece of wood being used for a stud.

The symbol is placed every 19 and 3/16th inches (or 19.2 inches). So you will find 5 of these symbols in an 8 foot span: 19.2 inches, 38.4 inches, 57.6 inches, 76.8 inches and right at the 8 foot mark. This 8 feet is important because that is the length of a sheet of plywood. So you will have 6 total joists supporting one 8 foot sheet of plywood.

Black diamond found directly at 8 foot mark.

“I” shaped floor joists are much stronger then traditional solid lumber joists. This means they can support more weight and have different spacing requirements. So when using these black diamonds you are able to use less joists with no loss of support.

Floor boards spaced out at 19.2 inches.
19.2 inch spaced floor boards

These diamond symbols allow contractors and others building structures to quickly make marks and place joists/trusses at the necessary length. This is especially helpful for roofers who have to quickly place trusses when building a house or shed.

Other uses for black diamonds

Though less common there are some other uses that the black diamonds may come in handy for.

One of these includes putting a chimney in between studs in your house. When using concrete blocks to make your chimney it is imperative you place studs 19.2 inches apart at least.

Standard concrete chimney that measures 16 and 3/4th inches.
Standard concrete chimney

A standard concrete block chimney uses 2 bricks side by side. This will be ~16 inches wide. That means 2 concrete blocks will not fit between a standard stud placement in a wall which is 16 inches wide (16 inches on center). With traditional center stud placement there will only be 14.5 inches between studs.

Space between 16 inch studs is 14.5 inches.

When using the 19.2 inch stud placement as represented by the black diamond you will have 17.7 inches between studs. This allows plenty of space for 2 concrete blocks needed to build the fire place.

Space between 19.2 inch stud is 17.7 inches.

You can also use the black diamond for stud placement in smaller structures that have less load to bear. In general when building a house studs are placed every 16 inches. This is important to stick to as walls in houses bear a lot of load. However, when building structures such as a shed you can space the studs out a bit to save materials and some money.

Small shed that has studs placed every 24 inches
24 inch stud placement for a small shed

It is highly recommended that you check your local building codes and requirements prior to doing any building.

Other symbols on tape measures

Another commonly found symbol on a tape measure is a red rectangle often around a number. This represents the most common distance for stud placement to build walls. This will be found every 16 inches. On my Stanley tape measure it not only has a rectangle around 16 inches, but also actually says STUD.

Stanley tape measure with 16 inch marked by red rectangle and the word STUD.

Again this takes the guess work out and allows for speed when installing studs. It can be very helpful and useful for contractors.

As a DIYer if you are not installing walls this can be helpful for finding studs when you need to install something heavy.


Studs are the vertical members of the walls. They are what the drywall or sheet rock is attached to and help provide structural support.

Studs are most commonly placed at 16 inches. This provides the most structural support and strength for walls. With that being said it requires a lot of lumber and can get expensive. Other commonly found stud placements include 19.2 inches or 24 inches. Both of which you will use less lumber and be cheaper.

Graph showing the distance between studs and how many studs there will be in an 8 foot span.

If you use the 19.2 inch stud placement technique you will save about 15% on cost (compared to the 16 inch method). Then if you use the 24 inch stud placement, you will save about 33% on cost (compared to the 16 inch method).

There is a lot more information out there when it comes to stud placement, and I recommend you do further research before choosing a technique for your structure.

Again I cannot stress this enough: I highly recommend checking local building codes in your area prior to building any structures as some areas require certain stud distances for appropriate support.


  • Black diamonds on tape measure
  • Other common uses for black diamonds on tape measure
  • Other symbols on a tape measure
  • Studs

Did you find this helpful? If so please let me know in the comments.

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