Counting Coils - Active and Inactive

To count your spring`s coils correctly you need to be able to differentiate active coils from total coils. Active coils are the open wound coils carrying the load and deflecting under it. Total coils represent all the coils that make up your spring design. The type of ends (closed and ground/closed and squared/open/ double closed) will determine the number of active or total coils your spring has.

A coil is formed when the spring wire has been wound a full 360 degrees. There are open wound and close wound coils in the forming of a compression spring. The ends of your spring will usually be close wound while the middle coils are open wound. The closed ends will allow the spring to stand straight on a flat surface.

To count the total coils, you start on the second wire (where it has already made a full turn), thus creating the first coil. You continue counting up until the last wire of your spring. Once you’ve done so, count the closed coils on each end.

counting active coils

Most springs will have closed and squared ends which are one closed coil on each end of your spring. Closed and ground ends are the same as closed and squared, except the ends are ground so the spring can stand better. Double closed ends are two closed coils on each end, adding up to four closed coils in total. They are usually without grind but could be ground as well. The last type of ends are open ends where one or both ends remain open wound.

coil spring with closed ends

coil spring with ground ends

coil spring with double closed ends

coil spring with open ends

To properly count the amount of active coils on a compression spring, you must subtract the closed (inactive) coils on the ends from the total coils. If you have regular closed ends or closed and ground ends, you must subtract two inactive coils from the total coils. If you have double closed ends, you subtract four inactive coils. However, if you have open ends, all coils are open wound so all coils are active.

Compression springs may have different ends on each side. You can have a spring with one closed end and one open end, or have a spring with more than two inactive coils on the ends. Whatever the case, to get the number of active coils, you just have to subtract the number of closed coils.

If you have any further questions or concerns, feel free to contact us via email or phone. Our experienced engineers can help you calculate your spring design with precision and in a timely manner. If you have already calculated your own design, feel free to get an Instant Spring Quote or search our compression spring stock in the Spring Finder tool at the top of every page.