What Size Gas Struts Do I Need?
Getting this right is crucial because a strut that’s the wrong size can make your application unsafe, or may fail to do the job at all.
In this guide, we’ll walk you through how to determine the right size gas strut for your needs, including covering length, stroke, force rating, fittings, and more.
Here’s what we’ll cover:
- Why getting the right size gas strut is so important
- How to measure for a gas strut
- How to work out the force you need
- Common mistakes to avoid
Why Getting the Right Size Gas Strut Matters
Choosing the wrong gas strut is more than a minor inconvenience. It can lead to alignment issues, excess strain on hinges or panels, and even risk of injury if the strut fails under load.
Here are some issues a wrong-sized strut can lead to:
- Panels that won’t stay open or closed
- Lids that fly open too fast or won’t lift at all
- Increased wear and tear on brackets and fittings
- Poor alignment that affects aesthetics or functionality
A correctly sized strut, on the other hand, will provide smooth, reliable performance for years to come. If you’re planning to install or replace your struts, start by understanding the key sizing factors.
Key Factors to Consider When Sizing
Each gas strut must be chosen based on your application’s specific requirements in order for it to be fit for purpose. Here’s what to look for, and why.
Extended and Compressed Length
The **extended length** is the full distance between mounting points when the strut is fully open. To measure this, check the distance between the hinge and the open mounting point of your application.
The **compressed length** is how long the strut is when fully closed. Measure the distance between mounting points when the lid, door, or panel is closed. These measurements are crucial to ensuring your strut fits and operates within the correct range of motion.
Stroke Length
**Stroke** is the difference between the extended and compressed lengths. It defines how far the piston rod travels.
To determine the correct stroke, calculate how far your panel or lid needs to move between open and closed positions. The stroke length should allow the strut to complete this movement without fully bottoming out or being under-extended, both of which can damage the strut or affect performance.
Force Rating
The **force rating**, typically measured in Newtons (N), tells you how much pushing force the gas strut provides. Getting this right is essential for safe and smooth operation.
To estimate what you need, start with the weight of the panel or object being lifted, the distance of the mounting point from the pivot, and how many struts you plan to use. Use the formula (panel weight × pivot distance × gravity) ÷ (number of struts × effective arm length), or consult an online calculator.
If you’re replacing an existing strut and its application hasn’t changed, you can use the printed rating as a reference.
End Fittings and Mounting Points
End fittings connect the strut to your application and help determine its range of motion. Ball sockets, brackets, and eyelets all serve different functions.
To figure out what you need, look at your existing fittings or measure the mounting points on your application. Consider the movement required and whether the fittings will allow that movement without interference, then ensure compatibility with your brackets and orientation.
How to Measure for a Gas Strut
If you’re not sure what size you need, the best place to start is with measurements. Whether you’re replacing an old strut or sizing one for a new build, here’s how to do it.
Measuring an Existing Strut
If you still have the old strut, it makes your job a lot easier. Simply measure the full extended length (from the centre of one end fitting to the other) and the stroke (by fully compressing and measuring the difference). Check the printed force rating if visible. Also note the type and size of end fittings.
For more information, check out our guide to measuring gas struts.
Measuring from Your Application
If the old strut is missing or you’re working on a custom project, you’ll need to measure the distances between mounting points in the fully open and fully closed positions. You can then calculate required stroke, compressed length, and extended length.
How to Work Out the Force You Need
Force rating is the trickiest part to estimate. It depends on the weight of the object being lifted, the mounting angle, the pivot distance, and how far along the panel the strut is fixed.
There are some rules of thumb (e.g. 60% of the panel weight split between two struts), but for anything more precise, you can:
- Use an online calculator
- Contact customer support with your panel weight and dimensions
- Use the rating from an existing strut as a baseline, if the application hasn’t changed
Common Mistakes to Avoid
Sizing a gas strut might seem simple, but there are a few common pitfalls that can trip people up and lead to more problems later in the process. Here's what to watch out for:
- Don’t guess the force rating! If in doubt, ask the supplier as they’ll be able to help
- Don’t measure the full body: for accurate measurements, always measure between the centres of end fittings
- Don’t mismatch end fittings: choosing the wrong type can affect how your strut functions or fits, so be consistent
- Don’t overestimate the required force: using a strut that’s too strong can be just as unhelpful as one that’s too weak, so get an accurate measurement for this
If you're stuck, don’t guess. Get in touch with us with as much information as possible - the weight of the panel, the distance between mounting points, and the general use case - and let us recommend the right size and force rating.