Measuring Screws and Bolts: the Basics

Deb C.

Finding the right length screws and bolts does not have to be a headache. Let’s discuss a few tips on how to measure correctly.


If the head is meant to sit above the surface of the item you are screwing it into, you measure it from under the head to the bottom. If the head is countersunk, then you measure from the top of the screw to the bottom. Countersunk screws end up being level with the surface material you are screwing them into. Countersunk screws usually have a round or oval head. These measurements hold true for all wood, metal and machine screws.


Hex, carriage, sex and lag bolts are all measured from under the head to the end of the screw. Eye bolts are measured from under the eye. Hanger bolts are measured end to end. Shoulder bolts are measured by the length of the shoulder.

If you have more questions about bolts and screws, you can ask questions at your local hardware store. Many internet sites will also have suggestions and tips on what screw or bolt will be right for the projects you will be using them for.