Fastener Measuring

How Do I Measure Bolts?

Measuring Bolts and Screws

If you searched "How Are Fasteners Measured?" then you have come to the right place! Most commonly, screws and bolts are identified by diameter (of the threaded portion), thread pitch, and length. Length is measured from the point at which the head sits flat with the surface, to the tip of the threads. Hex, pan, truss, button, socket cap, and round head screws are measured from right under the head to the end of the threads. Flat head screws are measured from the top of the head to the tip of the threads. Oval head screws are measured from the beginning of the undercut on the head to the tip of the threads. Headless fasteners, such as socket set screws or dowel pins are measured from top to bottom. Nuts and washers are measured by inner diameter. Rivets are measured by diameter and grip range. And so on...

Standard (Imperial or Metric), diameter, thread pitch, shank length, grade, head and thread length are all measured fastener features. Measuring fasteners is surprisingly simple. Different tools exist to help you measure screws, nuts, washers, bolts, rivets, etc. It is important to have the right tools and know how to measure fasteners. For example, you cannot measure a rivet with a ruler. This section was created with measuring in mind. Albany County Fasteners created this fastener measuring page to shed some light on fastener measuring through both pictures and videos. If you're still having trouble measuring your fasteners, reach out to us! We would be more than happy to help.

Dissecting Fastener Names and Titles

1/4" - 20 x 2 304 Stainless Steel Phillips Pan Head Machine Screws
Diameter Thread Pitch Length Material Drive Head Type
Fastener Breakdown Diagram

Length & Proper Measuring

It is important to measure the length of a screw correctly for it to fit your application. An incorrectly measured screw can end up hindering a projects timeline. If the fastener is measured incorrectly, you may end up with fasteners that are too long or too short for your needs. To that end, we have created these diagrams to show you how to measure a fastener based on its type. These simple rules should help keep things straight!

Measure a Flat head screw

Flat heads are measured from the top of the head to the tip of the screw.
Measure an Oval head screw

Oval head screws are measured from the start of the undercut.
Measure a Hex head screw

Pan, Truss, Hex, Button, Socket Cap, and Round Heads are measured from right under the head.
Bolt Diagram


The diameter (aka. Thread Diameter) of a screw is the measurement of thickness of the threaded portion.

screw Diameter

Thread Pitch

Thread pitch represents the number of threads per inch. A UNC Coarse 1/4-20 screw has a threaded shank that is 1/4" in diameter and has 20 threads per inch. A UNF Fine 1/4-28 screw has a threaded shank that is 1/4" in diameter and has 28 threads per inch. Coarse threaded screws have fewer threads per inch. Fine threaded screws have more threads per inch.

thread pitch

Bolt Measuring Tools

Below is a video of us talking about one of our favorite products, the bolt/screw measuring gauge (which you can buy here). This is a product that we liked so much we use it in our own warehouse!

Not only do we offer a gauge for measuring a bolt / screw diameter and length, we also have a gauge for measuring threads! Available in both Standard and metric sizes, shop these Thread Detectives which can help you identify coarse or fine threads as well as the diameter. You can also use them to measure nuts!

How To Use A Fastener Measuring Tool

How to use a Fastener measuring tool

Measuring Rivets

One of the most common questions in the industry is how do I measure a rivet? Albany County Fasteners decided that it was time to clear up the confusion. Below are several resources that can come in handy when measuring rivets.

  • Mandrel - Long end that is broken off of the rivet during installation
  • Hat - Portion of the rivet that is inserted and expanded to fit a hole
stainless steel rivets

Understanding Rivet Grip Range

Here is an example of calculating rivet grip range using a:

6-6 = X-Y
Where X Represents Diameter in X/32 and Y Represents Max Grip Range in Y/16
(X=6, 6/32 = 3/16) Diameter = 3/16
(Y=6, 6/16 = 3/8) Max Grip Range: 3/8
6-6 = (3/16 x 3/8)
Grip Range .251-.375

Rivet Measuring Video

If you think rivet measuring is difficult, check out the tool we use in our own warehouse to identify different rivets. This Rivet Measuring Tool we've enjoyed so much we started carrying it on our website to bring the ease of use to you!

Rivet Sizing

How to use a POP Rivet measuring tool

Need more information on measuring rivets?

Want to learn more about Fasteners? Check out our Weekly Blog for new posts every Monday!