Free · Elasticity
Spring Stiffness Unit Converter
Convert a linear spring stiffness between eight metric and customary force-per-length conventions.
- Formula & worked example
- Private in your browser
- No signup
Calculator inputs
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How to use this calculator
- Enter the known values in the units shown. Results update as you type.
- Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
- Use the worked example to check the method. Reset restores the starting fields.
Private by default
Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.
Formula and method
1,000 N/m equals 1 N/mm, approximately 0.10197162 kgf/mm and 5.7101472 lbf/in.
k = force / displacement; 1 lbf = 4.4482216152605 N; 1 inch = 0.0254 m; 1 kgf = 9.80665 N.
Worked example
Enter these known values and leave the other values blank.
- Stiffness in newtons per meter
- 1000 N/m
- Stiffness in pound-force per inch
- 5.71 lbf/in
- Stiffness in pound-force per foot
- 68.52 lbf/ft
- Stiffness in kip-force per inch
- 0.00571 kips/in
- Stiffness in kip-force per foot
- 0.06852 kips/ft
- Stiffness in newtons per millimeter
- 1 N/mm
- Stiffness in kilogram-force per millimeter
- 0.10197 kg/mm
- Energy curvature in joules per square meter
- 1000 J/m²
Assumptions and limitations
- All eight fields describe the same nonnegative linear stiffness. A kip is exactly 1,000 pound-force, and kilogram-force uses standard gravity 9.80665 m/s².
- The retained kg/mm unit choice means kilogram-force per millimeter, not mass per length. The field label clarifies that convention.
- Joules per square meter is dimensionally equal to N/m. For spring energy U = ½kx², k is the second derivative of energy with respect to displacement.
- Conversions use exact international inch and foot and exact conventional force definitions. They do not predict spring stiffness from coil dimensions or material properties.
- Any field can be entered to recover all others; clear an entered value or lock it to keep a chosen reference.
Common questions
Is kg/mm a mass density?
In this spring convention it means kgf/mm, using kilogram-force rather than kilogram mass.
Is kip a mass unit?
Here kip means 1,000 pound-force. It is a force unit in the stiffness numerator.
References
Correct four customary conversion factors to exact conventional pound-force and international length definitions, while retaining all eight synchronized fields and every inverse relationship. This unit converter supports nonnegative ordinary spring stiffness.