# Tension Spring Force Calculation

## Definition: The calculation of a tension spring’s force in regards to spring rate and initial tension.

The calculation of a tension spring’s force depends on two values which are rate and initial tension. Extension springs already have force stored in between its coils before it is even extended. This is why we must add that initial tension to the calculated amount of force per distance traveled based on spring rate. This can all be calculated using our extension spring calculator, Spring Creator by inputting only a few dimensions like the hook type of your preference, wire diameter, outer diameter, length inside hooks and material type.

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Extension Spring Calculator Instructions

To begin the tension spring force calculations you must know how much initial tension your spring already has gathered in its coils as well as your spring’s working loads. You will subtract the initial tension from the load and then divide the result by the distance traveled. The distance traveled is the difference between your spring’s extended length and the length inside hooks in its free estate. Doing so will give you your spring’s rate as shown in the formula and diagram provided.

Rate = (Load – Initial Tension) ÷ Travel

k = (L – IT) ÷ T