A flathead screwdriver is one of the most basic tools ever created, and it comes in a variety of screw size and lengths, each designed to serve a specific purpose, although they are primarily used in wood work.
The name is a little misleading because a flathead screwdriver can also be used as a miniature pry bar, scraper, or chisel. To get the most out of your tool for any task, it is best to select the size. This flathead screwdriver size guide will explain everything you need to know about the various types available.
Phillips screwdrivers are also common, but you can’t use them for anything other than what they’re designed for because of their design. A Phillips’s head is made to fit Phillips drives. (Find the Best Professional Screwdriver Sets)
While Phillips screwdriver sizes fit a certain Phillips head, you’ll find Phillips screwdrivers easier to find the right Phillips screwdriver for the job. Here, in our guide, we’ll stick to flathead screwdrivers as it can be a challenge to get the one that fits to save damage and harm.
By the end, you’ll see that you won’t need to know Torx screwdriver sizes, Allen wrench sizes, or even Robertson screws. While they are all common screw head shapes, they are not as common as the humble flathead screwdrivers.
What is the most common flat head screwdriver size?
A slotted screwdriver is another name for a flathead screwdriver. This is due to the driver’s flat tip being designed to fit snugly into the slot of a screw to tighten or loosen it. A slotted screw is one of several types of screws, including the more common Phillips head and the slightly less common square head. In contrast, hex screws require a six-sided driver known as a hex wrench or an Allen wrench.
Slotted screwdrivers work best when they fit snugly into the slot of the screw. A screw with a 14-inch wide head, for example, cannot be turned easily with a driver that is only half as wide. Similarly, for best results, the tool’s thickness should match the thickness of the slot on the screw head.
Flathead Screwdrivers Come in a Variety of Sizes
Flat blade screwdriver sizes range from millimeters to larger fractions of an inch. Each screwdriver has two dimensions: the shaft length and the tip width of the head.
The following flat tip screwdriver sizes are available in inches: 3/32 by 1 1/2, 3/16 by 1 1/2,
1/8 by 4, 3/16 by 4, and 1/4 by 4.
The first number represents the width of the driver head, and the second size represents the length of the shaft. The longer the shaft, the greater the ability of the screwdriver to reach into tight spaces.
This is especially handy when doing automotive work, as screws are frequently placed far back in an engine block. Use a tool with a shorter shaft if you can reach the head of a screw without using a long one. The shafts of stubby slotted screwdrivers are 1 1/2-inch long. They’re ideal for close-up work.
Flathead Screwdriver Sets
Flathead screwdrivers can be purchased individually, but having a set is the best way to ensure that you cover all of your bases when driving and removing screws. A screwdriver set may contain only flathead screwdrivers or a combination of flathead and Phillips head screwdrivers. A set includes a good selection of drivers, including at least one with a short shaft, one with a long shaft, and several in between.
Standard slotted screwdrivers are measured in inches and fractions of inches. A set of millimeter-sized tools is useful for precision screws such as those found on glasses, watches, and small electrical components. (Read Different Types of Ratchets)
Here you can find a rare flat head screwdriver size chart of flat head screwdriver sizes mm and SAE.
| Tip Width (SAE) | Tip Width (Metric) |
|---|---|
| 0.8 mm | |
| 1 mm | |
| 1.2 mm | |
| 1.5 mm | |
| 1.8 mm | |
| 2 mm | |
| 3/32" | 2.5 mm |
| 1/8" | 3 mm |
| 3.5 mm | |
| 5/32" | 4 mm |
| 3/16" | |
| 4.5 mm | |
| 5 mm | |
| 7/32" | 5.5 mm |
| 6 mm | |
| 1/4" | 6.5 mm |
| 5/16" | |
| 3/8" |
What is a #2 Flat Head Screwdriver?
These are commonly referred to as slotted screwdrivers and have a wedge-shaped blade.
Sadly, the way flat head screwdrivers are measured can be annoying, as the tip thickness is rarely provided.
The good news is that the two measurements to find the common sizes include the width of the tip and the length of the shank. These measurements are presented in width by length (for example, 1/8′′ x 4′′).
The shank length determines whether the screwdriver can fit into a deeper recess (ideal for automotive work) or if it works best in tight spaces with little room for your hand.
Because the length of the handle is proportional to the length of the shank, short-shanked drives have short handles as well. However, for some, it may not help determine if their screwdriver offers the right fit for their screw sizes.
Screws, unfortunately, don’t have any markings to show their size after you open the pack.
How Do I Know What Size Screwdriver I Need?
Flathead or Slot: The oldest and most inconvenient type of screwdriver bit configuration. It is not possible to use power drivers. Too much power and the tip of the screwdriver can jump from the slot. Likewise, when trying to tighten or loosen using these tools,
Phillips: Because of its larger surface area, which provides more torque to the screw head and does not slip as easily as the slot, it is popular and ideal for precision work. It is also less likely to damage the screw head, bit, or work surface. (Read Allen Key Size Chart Pdf )
Hex or Allen: Hex keys are good for non-slip as they fit inside the screw and can withstand more torque than other configurations. It was developed in Europe and has been extensively adopted for furniture, and automotive machine screws use.
Torx Drives: The Torx drive (star drive), commonly like the Allen or Hex bolts, can withstand higher torques with a longer lifespan. The Torx is the least likely to slip because of its larger surface area. Torx screws are widely used in automobiles, appliances, computers, and electronics. Torx drives have different numbers based on the distances of two opposing points. It is also designed not to over-tighten as the head can break off. (Read Socket Conversion Chart)
Robertson Screw: The Robertson screw, commonly referred to as the Square drive screw, is different types as they offer a ‘stick fit’ Robertson drive onto the screw head and are held in position on the tip by the Robertson drives. They also come with a numbering system and a color code size chart.
What is the Smallest Size Flat Head Screwdriver?
Here you can find the full range of screwdriver set sizes. However, not everyone uses screw sizes that meet the full range of table wood screw. (Read Craftsman Socket Sizes Chart)
Slotted Precision Sizes Chart
| Tip Width (SAE) | Width (Metric) |
|---|---|
| 0.8 mm | |
| 1 mm | |
| 1.2 mm | |
| 1.5 mm | |
| 1.8 mm | |
| 2 mm | |
| 3/32" | 2.5 mm |
| 1/8" | 3 mm |
| 3.5 mm | |
| 5/32" | 4 mm |
Slotted Standard Sizes Chart
| Tip Width (SAE) | Tip Width (Metric) |
|---|---|
| 3/16" | |
| 4.5 mm | |
| 5 mm | |
| 7/32" | 5.5 mm |
| 6 mm | |
| 1/4" | 6.5 mm |
| 5/16" | |
| 3/8" |
Using the incorrect screwdriver bit for your screw head can mean the difference between success and failure.
Choose a bit size that fills the screw head. A bit too large or too small will not seat properly, resulting in a stripped screw. The chart below shows the correct screwdriver bit for the most common screw gauges. You can avoid stripped screws, broken bits, and damaged work surfaces by using the correct screwdriver bit, pre-drilling a pilot hole, and using the correct speed and pressure on your drill.
While flat head screws are no longer widely used in residential construction, they can still be found in furniture construction, small cabinetmaking projects, and some electrical applications—which means flat head screwdrivers are useful for more than just prying paint can lids off.
Flat-head screwdriver bits are available for ratcheting screwdrivers and drills, but keeping a few flat manual screwdrivers in your tool bag is a good idea. They’ll be labeled with the size of the tip as well as the length of the steel shank. Tip sizes vary from a few millimeters to an inch or more. Choose a screwdriver that matches the width and depth of the slot on the screw head in question when matching it to a flat screw.
Screw Gauge and Point Size Screwdriver Chart
| Slot/ Flathead | Philips | Roberston/ Square Recess | |
|---|---|---|---|
| 2 | ⅛” / 3.2mm | #1 | #0 |
| 3 | 5/32” / 4.0mm | #1 | #0 |
| 4 | 3/16” / 4.8mm | #1 | #0 |
| 5 | 3/16” / 4.8mm | #2 | #1 |
| 6 | ¼” / 6.4mm | #2 | #1 |
| 7 | ¼” / 6.4mm | #2* | #1 |
| 8 | 5/16” / 7.9mm | #2 | #2 |
| 5/16” / 7.9mm | #2 | #2 | |
| 10 | 5/16” / 7.9mm | #2 | #2 |
| 12 | ⅜” / 9.5mm | #3 | #3 |
| 14 | ⅜” / 9.5mm | #3 | #3 |
As you can see from the above, there is no number 1 screwdriver size in mm.
