Screw Size report
One of the popular items in the tool shed of any DIY enthusiast is screws, we can also see different screws in daily life, but few people learn the details about various screw sizes and types. They come in different sizes and shapes.
When it comes to screws, there are two primary areas where people get confused. There are sheet metal screws and wood screws. Another is understanding the difference between metric screw sizes and imperial screw sizes.
Knowing how to find the diameter and length of the fasteners you need is an important first step in acquiring the correct parts. Having the correct screw sizes for your particular repair or building task is essential. The following article provides a detailed screw size chart for reference and a screw measuring guide.
Screw Size Guide
If you have some loose screws but need more of the same kind, you will need to know their size. Measure your old screws and check the corresponding standard screw size table. This way, you can make sure you get the exact size of screws when you go shopping for new ones.
Screw Size Chart
Screws with a diameter smaller than 1/4" have a nominal size indicated by a number, such as #8 or #10. 1/4" and larger diameters are shown as inches.
Suppose the screw size includes a dash with a number following it, the number of threads per inch. Usually, tpi is only shown with machine screws or other fasteners with machine screw threads.
| THREAD DIAMETER | |||
| Size | Nearest Fraction | Inch | Millimeter |
| #0 | 1/16 | 0.06 | 1.5 |
| #1 | 5/64 | 0.07 | 1.8 |
| #2 | 3/32 | 0.08 | 2.0 |
| #3 | 7/64 | 0.09 | 2.3 |
| #4 | 7/64 | 0.11 | 2.8 |
| #5 | 1/8 | 0.12 | 3.1 |
| #6 | 9/64 | 0.13 | 3.3 |
| #8 | 5/32 | 0.16 | 4.2 |
| #10 | 3/16 | 0.19 | 4.8 |
| #12 | 7/32 | 0.21 | 5.5 |
| #14 | 1/4 | 0.24 | 6.3 |
Fastener thread pitch
The thread spacing is also called the thread pitch.
| Pitch(mm) | Pitch(inches) | Threadsper Inch |
|---|---|---|
| 0.2 | 0.0079 | 127.00 |
| 0.25 | 0.0098 | 101.60 |
| 0.3 | 0.0118 | 84.67 |
| 0.35 | 0.0138 | 72.57 |
| 0.4 | 0.0157 | 63.50 |
| 0.45 | 0.0177 | 56.44 |
| 0.5 | 0.0197 | 50.80 |
| 0.6 | 0.0236 | 42.33 |
| 0.7 | 0.0276 | 36.29 |
| 0.75 | 0.0295 | 33.87 |
| 0.8 | 0.0315 | 31.75 |
| 1.0 | 0.0394 | 25.40 |
| 1.25 | 0.0492 | 20.32 |
| 1.5 | 0.0591 | 16.93 |
| 1.75 | 0.0689 | 14.51 |
| 2.0 | 0.0787 | 12.70 |
| 2.5 | 0.0984 | 10.16 |
| 3.0 | 0.1181 | 8.47 |
| 3.5 | 0.1378 | 7.26 |
| 4.0 | 0.1575 | 6.35 |
| 4.5 | 0.1772 | 5.64 |
| 5.0 | 0.1969 | 5.08 |
| 5.5 | 0.2165 | 4.62 |
Metric Screw Size
The size of a metric screw or bolt is specified as diameter, pitch and length, in millimeters. And metric screws are usually classified as either coarse or fine, referring to their thread pitch. You can check the below chart to know the metric screw sizes.- M = Metric thread designation
- 14 = Nominal diameter, in millimeters
- 2.0 = Pitch (distance from thread to thread), in millimeters
| Size | Series | Thread | Pitch(inches) | Threadsper Inch |
|---|---|---|---|---|
| M14-2.0 | Metric | Coarse | 0.079 | 12.7 |
| 9/16-12 | Inch | Coarse | 0.083 | 12 |
| M14-1.5 | Metric | Fine | 0.059 | 16.9 |
| 9/16-18 | Inch | Fine | 0.056 | 18 |
| M3.5-0.6 | Metric | Coarse | 0.024 | 42.3 |
| 6-32 | Inch | Coarse | 0.031 | 32 |
| M3.5-0.35 | Metric | Fine | 0.014 | 72.6 |
| 6-40 | Inch | Fine | 0.025 | 40 |
Types of US Screws
- Wood Screws
They are designed for connecting items to a wooden base. Wood expands and shrinks depending on the surrounding temperature. It means a specialized screw is required for wood applications. The best options are screws that bend before snapping. Wood screws have this capability, and that is why they are not used on sheet metal. The wood screw comes in various sizes provided in the tables found later in this guide.
- Sheet Metal Screws
They are typically sturdier and stronger than their wooden counterparts. They can be used in other materials apart from metal as they will stay strictly in place once screwed on.
How to Measure Screws
Measuring the screws is pretty easy. You only need a measuring tape or a ruler and the screws in question, and then make sure to measure the screws correctly using the imperial or metric system.
Diameter of Screws
To measure the diameter of screws, you measure the distance from the outer thread on one side to the outer thread on the other side. It is called the diameter and will usually be the proper size of the bolt. You can also measure from the bottom cavity of the threads from one side to the other to find the minor diameter.
Length of Screws
Length is the distance from the flat part of the head to the tip or blunt end of the screw or bolt. Almost all screw head types will either be flat on the top or the bottom.
Count the number of threads in 1 inch
Lay the screw next to a ruler or measuring tape and hold it steady. Count the number of threads in the space of an inch to get the thread spacing for screws in the imperial system.
