Bolts and screws are integral parts of fastening or putting together things. Several people assume that these two materials are the same, but they are different. Physically, they look similar. They are still unique fasteners in terms of application.
Screws are very versatile, making them a popular choice among people. The threads provide a sturdy grip, allowing them to meet the requirements of any project. They come in several types and sizes, which you can use in metal and wood. Other types are used for drywall and concrete. Screws are self-tapping, but you still have the option to drill a hole for it. Should you decide to go with the latter, it is less time-consuming to drill all holes first before installing the screws.
Summary
Metric & standard bolt screw sizes are determined by length and thread count. The easiest way to figure those out is to consult our screw size chart below. However, here’s a quick overview from the chart:
- The M2 screw size has a diameter of 1/16 inch.
- The M4 screw size has a diameter of 7/64 inches.
- The M5 screw size has a diameter of 1/8 inch.
Table of Contents
Standard & metric screw size chart
Here’s the standard & metric screw size chart you need to help you find the right products at the shop! It doesn’t matter if you’re working outside or on furniture. ASME is the organization that is in charge of a lot of the standardization work. These standards dictate things like thickness and screw thread.
| STANDARD SCREW SIZES & THREAD DIAMETER CHART | ||||||
| Size | Millimeter | Inch | Nearest Fraction | Major diameter | Pitch diameter | Minor diameter |
| #0 | 1.5 | 0.06 | 1/16 | |||
| #1 | 1.8 | 0.07 | 5/64 | |||
| #2 | 2 | 0.08 | 3/32 | |||
| #3 | 2.3 | 0.09 | 7/64 | |||
| #4 | 2.8 | 0.11 | 7/64 | |||
| #5 | 3.1 | 0.12 | 1/8 | |||
| #6 | 3.3 | 0.13 | 9/64 | |||
| #8 | 4.2 | 0.16 | 5/32 | |||
| #9 | 4.5 | 0.177 | 11/64 | |||
| #10 | 4.8 | 0.19 | 3/16 | |||
| #12 | 5.5 | 0.21 | 7/32 | |||
| #14 | 6.3 | 0.24 | ¼ | |||
| 8-32 | 0.164 | 0.1437 | 0.1257 | |||
| 6-32 | 0.138 | 0.1177 | 0.0997 | |||
| 4-40 | 0.1112 | 0.0958 | 0.0813 | |||
| 10-24 | 0.19 | 0.1629 | 0.1389 | |||
| 10-32 | 0.19 | 0.1697 | 0.1517 | |||
| 2-56 | 0.086 | 0.0744 | 0.0662 |
M2
We use the M2 screw in small items, such as electrical equipment, cameras, and mobile phones. They’re also common in laptops and the like. The “M” corresponds to the outer diameter in the metric system, so an M2 has a diameter of 2mm. Do keep in mind that in reality, the actual diameter would vary between 1.9mm to 2mm because of manufacturing tolerances.
n. Some manufacturers offer non-standard pitches, so it is best to reach out to them for any concerns in customization. If the measurement reads M2 x 8, the diameter is 2mm and has a length of 8mm.
Brass, nylon, stainless steel, steel, aluminum, and titanium are a few of the materials used in fabricating this type.
M4
An M4 screw is slightly larger than an M2. The M4 comes in several lengths but shares the same diameter of 4mm. The M4 screw size in inches is the equivalent of 0.15748.
M5
The M5 screw size has a diameter of 5mm. The M5’s dimensions are significantly thicker than an M4 but can be used in several applications. Some have an anti-corrosive finish to prevent rust from building up.
The M5 screw size in inches is the equivalent of 0.19685 inches.
M6
The diameter of an M6 screw is 6mm. It comes in several thread pitches, such as 12-24 and 10-32. A sample application of an M6 is attaching the equipment to the vertical uprights of a rack. We typically use the threads mentioned above in rack applications.
M8
An M8 screw has a diameter of 8mm. It has a pitch thread of 1.00mm for fine and 1.25mm for standard.
M10
The M10 screw has the widest diameter among these six kinds. It has a diameter of 10mm and comes in several lengths. The M12 is even wider and can shoulder heavier loads.
How do you determine the one to get?
When looking into and determining screw size dimensions, there are two things you need to understand – the length and the thread count. The latter is also commonly referred to as threads per inch (TPI) or thread pitch. We use the TPI to determine the thread’s fineness. The number will also tell if a screw can thread through a bolt. To measure screw size, we take its diameter. If the measurement says 1/4-20, it means it has a diameter of 1/4 inch and 20 threads per inch. A ruler is all you need to determine thread count and size.
The first step in measuring the length is finding a surface to lay it down on an even surface. Start measuring wherever the head would rest when fully embedded into something. In some cases, you may need to hang it off the edge of a surface to lay it flat. Ones with a pan, round, or truss head should be measured from the bottom of the head to the tip. Ones with a flat or oval head should be measured from the top to the tip. Hex head ones are an exception to this rule, which means you need to measure from the bottom of the head.
Now that you know how to take the measurement, the next step is to place the ruler down the axis to get the thread count. For accuracy, count the first thread as zero. Within one inch of the length, count the number of thread gaps. Once you have these values, you can now divide the length by the number of thread gaps. If there are four thread gaps in a one-inch length, the thread pitch would be 0.250 inches (one inch / 4 thread gaps = 0.250 inches). In other words, the gap in between each thread is 0.250 inches, and it has a Thread Per Inch (TPI) of four.
Lay it down on a flat surface again. Using a ruler or measuring tape, get the measurement from one side of a thread to the other to get the diameter. The diameter in the imperial system is represented in either fraction of an inch or a gauge number. If you are using the metric system, use the cm or mm side of the ruler to measure the diameter. Keep in mind that when purchasing ones with measurements that are listed in the metric system, the initial number is the diameter.
