This calculator will calculate any of the values remaining by changing one of the variables then selecting the "calculate: button for the selected variable.
About Extension Spring Design: Most extension springs are wound with an initial tension. This tension is the force that holds teh spring coils wound together. The spring rate tends to be constant over the central 60 percent of the deflection range. When designing for a particular spring, design for critical loads and rates to be within the central 60% deflection and load range. Standard and custom springs are available. Exceeding manufactures maximum deflection almost always reduces usable spring life cycles.