Extension spring calculator
Calculate the rate, initial tension and maximum load of extension springs with hooks. Enter the dimensions and the hook-to-hook length.
mm
mm
mm
N
Result
Spring rate9.008 lbf/in [1.58 N/mm]
Max safe load11.206 lbf [49.85 N]
Max safe deflection1.044 in [26.53 mm]
Initial tension10 N
Spring index9.00
Extension springs work under pull load and carry an initial tension that must be overcome before the coils separate.
The tool estimates initial tension from geometry and validates that the hooks fit within the overall length.