Spring Constant

The spring constant is defined by Hooke’s law:

$k = \frac{F}{x}$

where $F$ is the applied force (N) and $x$ is the extension (m).

A larger spring constant means a stiffer spring that requires more force to extend by the same amount.

The spring constant is the gradient of the straight (proportional) section of a force-extension graph. Beyond the limit of proportionality, the spring no longer obeys Hooke’s law and the force-extension relationship is no longer linear.