Wood Screw Sizes Chart

January 22, 2023

You might be asking whether you can use all wood screws on wood. Of course, the answer is, “Yes, you can!” Nevertheless, it will be good to note that wood screws differ in length, diameter, and other aspects. Thus, you must choose the screws that are best suited for a particular application. Besides, you should select screws that correspond to the wood’s width. Furthermore, you should ensure that the screw you use supports the load the screws would bear.

When buying wood screws, for example, you might be asked about the gauge or diameter of the screw. You will often see the diameter or gauge of the screw in number forms like #6, #8, and #10. These numbers are related to the screw’s thickness. Yet, if you are engaged in fine woodworking, it will be best to use the #6 screw, while for general applications, the #8 gets widely recommended.

What Are Wood Screws?

Wood screws are screws that you can use primarily for securing connections between wooden materials. You can use them with softwood, hardwood, chipboard, and MDF. Besides, you will find different screw types, designed with features like shanks to prevent wood splitting, tips that imply you don’t need to predrill the materials, and twin threads for efficient driving.

You can also purchase wood screws with various head shapes and drive types. The most popular among these different varieties of screws are the ones with countersunk heads and the Pozidriv, which is the abbreviation for positive drive.

The main parts of the wood screws include the head, tip, and shank. For one, the shank gets partially threaded, which means the thread extends only to about three-fourths down the body of the shank. You will also find wood screws that feature a fully threaded shank extending to the tip of the screw.

Moreover, you will find tapered-head screws with the head blended with the shank. The point where the shank meets the wood screw’s head gets tapered. With this tapered design, the head can rest flush with the workpiece’s surface on which you install the screw.

Wood screws were originally wrought in steel or brass. They also came with a shaft that features increasing thickness near the head. Users of this screw type needed to drill pilot holes to ensure these screws snugly fit into the material. However, the modern wood screw features uniformly sized shanks, which does away with predrilling a pilot hole.

Examples of Wood Screw Sizing for Most Common Screw Sizes

When using screws, it is necessary to choose the best-suited screws for your projects. Carefully consider the thickness of the screws you would like to use, for the thickness should correspond with the wood’s width. Besides, the screws must be able to support the load’s weight.

You need to look at the gauge or diameter of the screws carefully. A number indicates the screw’s diameter or gauge. Examples of commonly used screws are #6 and #8. As the number increases, the thickness also changes. As mentioned above, the number 8 screw is best suited for general applications, while the number 6 is best for fine woodworking. The standard screw sizes are the following:

#4 Screws

The #4 screw is the most common size of wood screw that applies to small craft, attaching hinges, and jewelry boxes and other light-duty wood crafts. Its thread size is 0.112″.

#6 Screws

The #6 screw gets typically used for screwing together small objects. Yet, it doesn’t mean that it is the smallest screw you can ever buy. Its thread size is 0.13” or around 9/64th inch. Besides, you can buy this screw in ½” to 1-1/2” length. You can also use this screw mainly for drawer slides, hinges, light-duty jigs and fixtures, and toys.

#8 Screws

The #8 screw belongs to the most commonly used screws. It gets used for screwing together a variety of wooden objects. Its size in thread diameter is 0.16” or 5/32”. This screw is an all-purpose screw you can often find in light construction, furniture, and cabinets. It also ranges in length from 5/8” to 3”.

#10 Screws

The #10 screw features a larger diameter, reserved for heavy-duty jobs. Its thread diameter is 3/16th or 0.19″. You will often find this screw used in various construction jobs. It gets used in screwing heavy furniture. This screw ranges from ¾” to 4.”

How Do You Measure Wood Screw?

Two major factors determine the sizes of screws. First, there is the shaft length. Then, there is the diameter or thickness of the screws. So, if you look at the screw chart, you will often find these two factors to indicate the size of the screw.

The diameter and length of the screw often get measured or indicated using inches. Thus, in the screw size chart, you will see the length and diameter of screws in inches ranging from 0 to 24 inches. Besides, manufacturers often indicate the wood screw gauge in the screw box itself.

If the screws are not in the screw box, you can determine the screw size by measuring the screw manually. Get the thread’s width in fractions to figure out the diameter of the screw.

What Does the Screw Number Imply, and How do You Figure Out its Size?

The wood screw’s size gets indicated by its thickness and diameter (gauge) and the shaft’s length. These two factors are measured using inches. Nevertheless, you will find the gauge indicated in number. So, if it is your first-time purchasing screws, you might get confused a bit with the screw gauge or size number. Below is a short graph and chart of the wood screw sizing:

Screw Sizes	Nearest Fractional Size	Straight Pilot Bit (Hardwood)	Straight Pilot Bit (Softwood)
#2	3/32 inch	1/16 inch	1/16 inch
#3	7/64 inch	5/64 inch	1/16 inch
#4	7/64 inch	5/64 inch	1/16 inch
#5	1/8 inch	3/32 inch	5/64 inch
#6	9/64 inch	7/64 inch	3/32 inch
#7	5/32 inch	7/64 inch	3/32 inch
#8	5/32 inch	1/8 inch	7/64 inch
#9	11/64 inch	9/64 inch	1/8 inch
#10	3/16 inch	9/64 inch	1/8 inch
#12	7/32 inch	5/32 inch	9/64 inch
#14	¼ inch	11/64 inch	5/32 inch
#16	17/64 inch	3/16 inch	11/64 inch
#18	19/64 inch	7/32 inch	13/64 inch
#20	5/16 inch	15/64 inch	7/32 inch

You will see in this chart the closest fractional size column that refers to the screw size or gauge and the nearest fractional diameter of the screw shaft. The two other columns are there to enable you to figure out the drill bit you will use when you drill a pilot hole for a screw. You can choose between softwoods and hardwoods.

It will be good to note that the longer the screw, the better it can provide a stronger joint. Yet, your choice of screws should not be longer than necessary. Otherwise, they may break through the other side of the material.

Besides, it will be good to note that the thicker the screw, the stronger it can hold the joint. Yet, if it is too thick for the material, it might split the material.

Furthermore, you need to take into consideration the wood type you will be screwing. Moreover, you should consider whether you are inclined to make a pilot hole or not.

Drive Types, Head Types, and Screw Materials: What is the Difference?

The screw material usually refers to the material the screw is made of. The most common materials used for screws are carbon steel and brass for screws used for indoor applications. However, for outdoor, it is stainless steel. Besides, outdoor screws are often electroplated or galvanized coated to prevent deterioration and rusting.

Many screw manufacturers have developed their proprietary coatings, especially deck screws. Nevertheless, you will also find screws coated with various finishes like bronze, black oxide, and nickel for decorative purposes.

When it comes to drive type, you will find Slotted heads and Phillips styles. Yet, you will also find screws with square, hex, and torx/star heads. You will likewise find Phillips square head screws.

When it comes to head types, the most common types are round, flat, and oval, although you can also find other options. The flat head screws come with a conically shaped underside and flat top, allowing the screw to sit well and flush with the material for a smooth surface.

Oval head screws, on the other hand, come with a conically-shaped underside. They are flathead screws, likewise. Yet, they have decorative tops that don’t sit flush above the material surface.

Round head screws, however, are also flat on the head’s underside. Yet, they have domed tops sitting above the wood surface.

Different Parts of Wood Screw

Screws, though they are small, have various parts. Its anatomy consists of thread diameter, root diameter, length, and head diameter. Below is a short description of these different parts:

Thread Diameter

A number indicates the thread diameter (major diameter), wherein every number shows a specific thread diameter. So, if you see a thread diameter of 0.13 inches, it is a #6 screw. The thread diameter ranges in size from #0 to #14. You can also find larger sizes as indicated in the abovementioned chart.

Root Diameter

The root diameter refers to the shank of the screw beneath the thread. You will see the thread’s inner groove reaching the shank’s root diameter. Moreover, the shank diameter equals the threaded hole’s core diameter.

The root diameter, of course, is less important than the thread diameter, for its dimension is usually standardized, depending on the pitch and outer diameter. Nevertheless, for some users of screws, it is essential to know how much material the screw’s root will occupy.

Length

The length of the screw refers to how long the screw is. So, a half-an-inch-long screw is half an inch in length. If you buy a flathead screw, you can figure out the length by measuring the screw from the top of the flat up to the screw’s bottom. However, with a rounded head and Panhead, the length is usually calculated from the head’s bottom to the shank’s end.

Head Diameter

The head diameter refers to the head’s radius or diameter. The head, of course, sits at the screw’s top. This diameter will differ depending on the screw size and the job the screw performs. You will find wide-head screws, for example. You will also see a smaller head for less visibility.

Factors to Consider When Selecting Wood Screws

Although you may use all wood screws on wood pieces, screws are not similar to each other. So, when buying a screw, you must consider the screw size. Wood screws come in various sizes. You will find long and short screws. Besides, the screw diameter might also vary form one screw to another. You will find, for example, thick and thin screws.

Aside from the sizes of screws, you should also consider the material out of which the screw is made of. As mentioned above, screws are mostly wrought in steel. However, you will find high-carbon and stainless-steel screws. Other screws might be wrought in aluminum, brass, or titanium.

Furthermore, you should choose wood screws that come with the right drive recess. The drive recess, of course, is the grooved pattern or groove in the screw head. Thus, when installing a screw, you must place a bit onto the screw head’s drive recess. Afterward, you can turn the screw.

Conclusion

Wood screws have a long history dating back thousands of years ago. They have been reliable in joining wood pieces together. Screws, however, have evolved over time and now you will find a variety of screw options when purchasing screws. Besides, screws have become easily available, thanks to commercialization of screws. Yet, there were times when screws were very precious like precious stones.

So, after reading this post, you will become cognizant of the different sizes of screws and the different parts of screws that you need to consider when shopping around for the needed screws. Knowing the wood screw sizes chart and understanding it will allow you to choose the right wood screw for your needs.