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Attention! Input results shown will be +/- 10% from middle value. Hint: The closer your min and max inputs are, the more accurate your results will be!

Outer Diameter:

to

inches mm

Inner Diameter:

to

inches mm

Free Length:

to

inches mm

Wire Diameter:

to

inches mm

Total Coils:

to

Rate: ? Spring rate or spring constant: The amout of force required to move the spring 1 inch of distance or in millimeters the amount of force required to move the spring 1 millimeter of distance.

to

lbs/in N/mm

Info! Please fill in one or more fields to narrow down your search.

Max. Load: ? The maximum amount of force or load you can place on this spring. If you put more force than this you will distort or fatigue the spring.

to

lbs N

Max. Deflection (Max. Travel):

to

inches mm

Solid Height:

to

inches mm

* Required Field

Attention! Input results shown will be +/- 10% from middle value. Hint: The closer your min and max inputs are, the more accurate your results will be!

Outer Diameter:

to

inches mm

Length Inside Hook:

to

inches mm

Wire Diameter:

to

inches mm

Info! Please fill in one or more fields to narrow down your search.

Max. Load: ? The maximum amount of force or load you can place on this spring. If you put more force than this you will distort or fatigue the spring.

to

lbs N

Max. Deflection (Max. Travel):

to

inches mm

Initial Tension: ? The force required to seperate the coils of an extension spring before the spring will extend.

to

lbs N

Rate: ? Spring rate or spring constant: The amout of force required to move the spring 1 inch of distance or in millimeters the amount of force required to move the spring 1 millimeter of distance.

to

lbs/in N/mm

* Required Field

Attention! Input results shown will be +/- 10% from middle value. Hint: The closer your min and max inputs are, the more accurate your results will be!

Outer Diameter:

to

inches mm

Inner Diameter:

to

inches mm

Free Position or Leg Position in degrees: ? Free Position or Leg Position in degrees

degrees

Total Coils:

to

Wire Diameter:

to

inches mm

Body Length:

to

inches mm

Info! Please fill in one or more fields to narrow down your search.

Max. Torque: ? The amount of force applied to a torsion spring to radially move the springs leg a certain amount of degrees.

to

lbs N

Max. Deflection (Degrees of travel):

to

degrees

Rate: ? Torsion spring rate is the amount of radial force required to move the spring 360 degrees of distance. Divide the spring rate by 360 degrees to get the rate per degree

to

in-lbs./deg. N-mm/deg.

Leg Length: ? Both legs are equal in length

to

inches mm

* Required Field

Attention! Input results shown will be +/- 10% from middle value. Hint: The closer your min and max inputs are, the more accurate your results will be!

Small Outer Diameter:

to

inches mm

Large Outer Diameter:

to

inches mm

Free Length:

to

inches mm

Info! Please fill in one or more fields to narrow down your search.

Rate: ? Spring rate or spring constant: The amout of force required to move the spring 1 inch of distance or in millimeters the amount of force required to move the spring 1 millimeter of distance.

to

lbs/in N/mm

Total Coils:

to

Solid Height:

to

inches mm

Wire Diameter:

to

inches mm

Compression Spring Rate

Compression Spring Rate

Compression spring rate refers to the constant force exerted by a compression spring for each inch or millimeter of travel when subjected to an applied load. It's a crucial spring specification that helps determine whether the compression spring can meet the working loads when installed in an application. This force remains constant, with the load and travel increasing consistently. The rate is calculated based on the spring's physical dimensions, such as wire diameter, active coils, and outer diameter. Additional dimensions like inner diameter, mean diameter, and index correction can also be determined using these primary dimensions.

The Compression Spring Rate Formula

To calculate the spring rate of a compression spring based on its physical dimensions, including the material type, you can use the following formula:

k = Gd^4 / 8D^3N

Explanation of Symbols:

d = wire size (inches)
D = Mean Diameter (inches)
N = Number of active coils
D / d = Index correction
G = Shear Modulus of Material
k = Spring Constant

G-Value for Common Spring Materials

Music Wire = 11.5 x 10^6
Stainless Steel = 11.2 x 10^6
Phospher Bronze = 5.9 x 10^6
Monel = 9.6 x 10^6
Inconel = 11.5 x 10^6
Copper = 6.5 x 10^6
Beryllium Copper = 6.9 x 10^6

How to Measure Diagram

diagram explaining how to measure a compression spring with lines and arrows signaling each dimension along with the name of each dimension

How to Calculate Spring Rate

To calculate the spring rate necessary to meet your working loads, simply divide the load applied to the spring by the expected travel or compression distance. The formula for compression spring rate is as follows:

Rate = Load ÷ Travel
k = L ÷ T

Let's illustrate this with examples:

Example 1.)

Suppose you have a heavy-duty spring with a free length of 1 inch and it's expected to compress by 0.2 inches under a 5-pound load. To determine the compression spring rate, divide the load (5 pounds) by the travel (0.2 inches), resulting in a rate of 25 pounds of force per inch of travel.

k = L ÷ T
k = 5 ÷ 0.2
k = 25 lbf/in

First of two examples showing a spring at its free length and the same spring next to is at loaded height to explain how to calculate spring rate.

Example 2.)

Consider a compression spring with a free length of 5 inches, which is expected to compress by 2 inches under a 20-pound load. Calculating the compression spring rate involves dividing the load (20 pounds) by the travel (2 inches), yielding a rate of 10 pounds of force per inch.

k = L ÷ T
k = 20 ÷ 2
k = 10 lbf/in

Second of two examples showing a spring at its free length and the same spring next to is at loaded height to explain how to calculate spring rate.