If you are wondering where to find spring compression calculators look no further. Planetspring.com offers a compression spring calculator
that was constructed with you in mind. We have made the simplest and most effective compression spring calculator on the web today.
This calculator will help you from A-Z with your coil spring design. Before you get started on your compression spring calculation you will
need to know how to measure a compression spring. Please see the picture at the top of the calculator or watch our “how to measure a
compression spring” video to learn how to measure number of active coils, wire diameter, free length, and outer diameter, because these will be
the 4 inputs needed to begin calculating spring rate. Compression springs are often metal springs.
In order to calculate your spring properly you will need to know the type of spring wire. For example, are you looking for music wire springs
or a stainless steel compression spring? Simply choose the type of wire and you are ready to calculate.
Once you have hit the calculate button you have created your compression spring design. You have outputs such as the spring rate and the
spring constant as well as any other output you will need. If you need help using the calculator or you would like to be walked through
the process before using the calculator please watch our “Compression spring Calculator Video” at the top of the page.
If you are a registered buyer with Planetspring.com our compression spring calculator offers an additional benefit.
Once you have hit the calculate button you will be given 19 outputs that add up to all of the dimensions a supplier needs to quote your job.
Therefore, once you have the outputs you simply copy and paste them right into the part description section of your RFQ. This allows those
buyers who do not have blueprints of their spring to have a complete design before posting a RFQ.
In order to completely understand your spring design you will need to understand the spring rate, load, and index of your spring.
The rate of your spring is a constant. This constant will let you know how much weight (pounds, ounces, grams, N/mm)
is needed to move the spring one inch (1”) or in the case of metric measurements 1mm of distance.
The load of a spring is how much force in weight (pounds, ounces, grams, N/mm) needed to move a spring a particular distance.
For example you have a 10” (inch) long spring and a rate of 10lbs/in. You want to know what the load is if you need to travel 3 inches.
So you take the rate (10lb/in) and multiply it by the distance you are traveling (3 inches). This will give you a total load of 30lbs.
Formula to determine load is:
Rate x Distance Traveled = Load
Also with a compression spring you will have a preload (L1) and a working load (L2). For example on our spring above our preload (L1)
would be 10lbs @ 9 inches loaded height. L2 would be 30lbs at 7 inches height if these are the heights in your design.
The next thing you want to remember when designing your spring is the index. The index of your spring will let you know the
stress level of your spring. This value is one of the outputs you will get from our calculator. Once you have calculated your spring
take a look at the “spring index”. If the value in that column is lower than a 4 you will have a very high stress spring with small amounts of travel.
This will cause the spring to become very fatigued and you will have spring failure. If your index is a 14 or higher your spring will be very wobbly.
An example of this would be a slinky. This type of spring can be made but will come at a high cost to you because it is very hard to manufacture.
If you would like optimum repeatability and a cost effective spring make sure your spring index is between 6 and 13.
Formula to determine index:
Index = mean diameter / wire size
Mean diameter = Outer Diameter - 1 Wire Diameter
Configuring a spring rate calculation by hand, calculating spring constant or calculating
any type of spring constant physics can be tricky.