How to Count Coils in a Compression Spring
When trying to find a stock compression spring, coil count can be a helpful factor. Whether you are looking to replace an old spring or find one that fits your application, knowing how many coils your spring has, can help determine if the spring will work. In some cases, it can be hard to determine the exact amount of coils if you are unsure of where or how to start counting.
Total Coils
The total number of coils is counted from the point where the wire has been wound a full 360º to form the coil. This means that you start at the second wire as shown in the diagram below. It describes how you would count the coils in a compression spring.
When the last coil you count doesn’t align with where the first one began, it means you have a fraction of a coil more. This can be 1/4 of a coil, 1/2 of a coil, etc.


Active Coils
Determining the difference between active coils and inactive coils is necessary because active coils are the ones that carry most impact in regards to the force the spring can withstand.
To determine the number of active coils you need to determine the type of ends your spring has. If it has double closed ends you need to subtract four coils from the total coil count. Should you have closed ends, you need to subtract 2 coils from the total coil count. If your spring has open ends, the total number of coils are all active so there is not further calculations done.


Inactive Coils
Inactive coils, also known as dead coils, are the coils at the ends of the spring that have no pitch between them. Inactive coils do not fulfill the function of storing and releasing energy, instead they are static. This is the case with closed and squared ends, where the end coils are inactive. In the case of closed ends there is one inactive coil on each end. In the case of double closed ends there is two inactive coils on each end. Closed and ground ends are simply closed and squared ends that are ground flat. Open end compression springs have no inactive coils because all the coils have pitch in between them. This means all the coils in open end compression springs are active coils.
For a more interactive demonstration of how to count a spring’s coils, you can watch the following video.