How to Calculate Compression Spring Strength

Compression springs are used for a variety of applications, from absorbing vibrations to providing reaction forces. A spring is designed with a specific strength, which is dependent on the material, the diameter of the wire and the pitch of the coils. The spring constant (k) is a measure of the strength of a compression spring and can be easily measured.

Instructions
1.Place the spring vertically on a flat surface. If the spring does not lay flat, apply a small amount of adhesive to the end of the spring to keep it from falling over.

2.Measure the height of the spring with a ruler.

3.Stack washers on the top end of the spring until the spring has compressed about halfway.

4.Measure the height of the compressed spring. Do not include the stacked washers in the measurement. Subtract the compressed height of the spring from the original height of the spring to get the spring displacement (x).

5.Place the stack of washers on the electronic balance and read its weight (F).

6.Calculate the spring constant (k) using the formula k = F / x. If the uncompressed spring has a height of 1 inch, the compressed spring has a height of 0.5 inches and a total of 0.25 lb of washers were placed on the spring to compress it, then k = (0.25) / 0.5 = 0.5 lb/in.