A Simple Guide to Flathead Screwdriver Sizes

Using a slotted screwdriver to loosen or tighten a screw.

One of the most basic tools ever designed, a flathead screwdriver comes in a variety of sizes and lengths, with each meant to serve a particular purpose. Its name is a little misleading, for a flathead screwdriver often serves equally as well as a miniature pry bar, a scraper, or a chisel.

To get the most effective use out of your tool for any given task, it is best to choose a size that is suitable. This guide to flathead screwdriver sizes will outline for you everything you need to know about the different types available.

Each size uses the same basic design, but the differences lie in the length of the shaft and the width and thickness of the driver itself.

Slotted Screwdrivers

Another way to describe a flathead screwdriver is to call it a slotted screwdriver. This stems from the fact that the flat tip of the driver is meant to fit snugly into the slot of a screw to tighten or loosen it.

A slotted screw is one of many kinds of screws including the equally-common Phillips head and the somewhat less common square head. There are also hex screws that require a six-sided driver known as a hex wrench or an Allen wrench.

Slotted screwdrivers work best when they fit appropriately into the slot of the screw. For example, a screw with a head that is ¼-inch wide is not easily turned by a driver only half as wide. Likewise, the thickness of the slot on the screw head should also be matched by the thickness of the tool for best results.

Flathead Screwdriver Sizes

Flathead screwdrivers range in size from mere millimeters up to bigger fractions of an inch. Two measurements are noted for each screwdriver: the length of the shaft and the width of the head.

Examples of flat head screwdriver sizes in inches include 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 while the second size indicates the shaft length. The longer the shaft, the farther the screwdriver can reach to tight spaces.

This is especially handy when doing automotive work, as screws are often placed far back in an engine block. If you can reach the head of a screw without the aid of a long shaft, it is better to use a tool with a smaller one.

Stubby slotted screwdrivers have shafts of 1 1/2. They are useful for close-up work. The downside to this type of screwdriver is that the handle is very stubby too. Screwdrivers with longer shafts have proportionately longer handles which enable you to get a better grip as you use it.

Flathead Screwdriver Sets

Flathead screwdrivers are sold individually, but the best way to cover all of your bases when driving and removing screws is to have a set. A screwdriver set can consist of just flathead screwdrivers or a combination of flathead and Phillips head varieties. In a set, you will get 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. However, having a set of miniature tools measured in millimeters is handy for precision screws such as those found on glasses, watches, and small electrical components.

Guide to Flathead Screwdriver Sizes FAQ

How do you know what size screwdriver to use?

When there are a bunch of different screwdrivers and screws in all sizes, how do you know which one to use for the job at hand? For starters, the size of the screws should be marked on the package they were purchased in.

Otherwise, look for the screw that fits the screw head precisely. If the screwdriver is a little too big or too small, you're using the wrong size.

How are flathead screwdrivers measured?

Screwdrivers are measured in two ways: the width of the driver head and the length of the shaft. The head is measured in millimeters, while the shaft is typically measured in inches.

How do you know screw sizes?

Screw sizes are measured in the diameter of the head and the length. The measurements are indicated by inches.

The size of screws is indicated in the boxes they come in when sold. Otherwise, you can try to measure screws to determine their size.

What is a standard flat screwdriver?

All flathead screwdrivers are made with the same basic design, so the only variation you can find in flathead screwdrivers is their size. The most popular size the 3.5mm screwdriver, with the 5.5mm size coming in as a very close second.

What are standard screwdriver bit sizes?

Flathead screws come in a wide variety of sizes, so there are a wide variety of drill bits that can be used with them. Look for flathead screws in 1/8-inch, 5/32-inch, 3/16-inch, and 1/4-inch most commonly.