How is the extended length of a gas spring measured?

Measure between the defined connection reference at each end while the spring is fully extended. For eyelets and ball sockets this is normally centre to centre. For threaded ends, state whether the reference is the thread end, shoulder or another point shown on the drawing.

Is gas spring stroke the same as extended length?

No. Stroke is the distance the rod travels between the extended and compressed positions. Extended length includes the cylinder, rod, end connections and the current extension, measured between defined reference points.

Can Gemini replace a gas spring when the label is unreadable?

Often, but the application must be reviewed. Send extended and compressed lengths, rod and cylinder diameters, both fittings, mounting photographs, panel weight, hinge geometry and opening angle. Do not estimate force from physical size alone.

Should I measure a gas spring while it is installed?

Photograph and record the installation before removal, but secure the load and remove the spring when necessary to reach its true reference points. Never place yourself beneath an unsupported lid or force a pressurized spring closed by hand.

Technical guide

How to Measure a Gas Spring for Replacement

To identify a replacement gas spring, record the fully extended and compressed reference-to-reference lengths, stroke, rod and cylinder diameters, force marking and both end connections. Photograph the label, fittings and mounting points. Matching length alone is not enough to confirm a safe replacement.

Published September 10, 20267 minute read

Prepared from Gemini's published technical documentation. Application-specific review is still required.

The short answer

Three points to understand before taking measurements or selecting a spring.

Measure between defined points: Use the centre of an eye, ball or mounting pin when that is the connection reference. State the reference used for threads or shoulders.
Record both lengths: Measure fully extended and fully compressed length with the same reference points. Their difference is the used stroke.
Copy the complete label: Record the manufacturer, part number and force in newtons when legible. Photographs reduce transcription and fitting errors.

Step-by-step method

Work in this order so the dimensions and application details stay connected.

Make the application safe
Support and secure the moving lid, hatch or panel before removing a spring. Do not rely on the remaining spring or a person to hold the load.
Photograph the installed spring
Capture the label, rod and cylinder, both end fittings, both mounting brackets and a side view of the complete mechanism.
Measure the fully extended length
Measure between the same defined connection points at each end. For eyelets and ball sockets, this is normally centre to centre.
Measure compressed length and stroke
Measure the same reference points with the spring fully compressed only when this can be done safely. Stroke is the change between the two measured lengths.
Measure the body and connections
Record rod diameter, cylinder diameter, thread sizes, hole or ball diameters, fitting lengths and any bracket offsets.
Record the application requirements
Include the moving weight, hinge position, opening angle, quantity, temperature, environment and what the spring must do through the full travel.

Choose consistent measurement points

The reference point depends on the connection at each end.

Extended and compressed lengths are only comparable when both measurements use the same reference points. Do not measure from the outside edges of fittings unless the drawing or manufacturer specifically defines that convention.

If the two ends use different connection types, identify each reference separately and include a labelled photograph or sketch. A few millimetres at either fitting can change whether the spring reaches its mounting points or bottoms out during travel.

Connection	Useful reference	Also record
Eyelet	Centre of the eye hole	Hole diameter, thickness and fitting width
Ball socket	Centre of the mating ball	Ball diameter and socket style
Clevis	Centre of the clevis pin	Pin diameter, inside width and thread
Rod-end bearing	Centre of the bearing bore	Bore size, width and thread
Threaded end	Defined thread end or shoulder	Thread diameter, pitch and exposed length

Extended length, compressed length and stroke

These three dimensions describe different parts of the spring's travel.

Extended length is the distance between the selected connection references when the spring is fully extended. Compressed length uses those same references when fully compressed. The difference between the two measurements is the used stroke.

Do not assume that a replacement can safely use every millimetre of nominal stroke. Internal construction, end fittings, brackets and the application geometry can impose limits. The assembly should not force the gas spring to act as the only mechanical stop unless Gemini has approved that use.

Measure in millimetres when possible and avoid rounding until the replacement is reviewed.
Keep the rod straight while measuring; bending or side load can distort the reading and indicates an installation problem.
If safe compression is not possible, provide the application dimensions and mounting-point travel instead of forcing the spring closed.

Find the force and part-number markings

The force is normally stated in newtons and cannot be identified from length alone.

Look around the cylinder for a manufacturer name, part number, date code and a value followed by N. Copy every character and photograph the complete label in even light. A worn spring may no longer produce its original marked force, so testing the old unit is not automatically the same as identifying its new specification.

If the label is missing or unreadable, do not select force from rod size or panel weight alone. Send the application geometry to Gemini or use the gas spring calculator for a preliminary hinged-panel estimate. Final force also depends on leverage, mounting position, friction, temperature and the desired opening and closing effort.

Replacement request checklist

Send the spring data and the mechanism data together.

Manufacturer, complete part number and force marking in newtons
Extended and compressed reference-to-reference lengths
Stroke, rod diameter and cylinder diameter
Connection type, dimensions and thread at both ends
Panel weight, hinge position, opening angle and number of springs
Clear photographs of the label, fittings, brackets and full application
Operating temperature, moisture or chemicals, cycle frequency and safety requirements
Required quantity and whether the replacement must match existing mounting points

Safety and replacement limits

A gas spring is a pressurized component, not a part to open or improvise around.

Do not drill, cut, heat or open a gas spring. Secure the moving load before removal and follow the product label and supplied instructions. Both end connections must be able to pivot without twisting or side-loading the rod during the complete movement.

A dimensional match does not confirm the required force, damping, material, pressure, mounting loads or safe operating behaviour. Gemini should review the complete application before the replacement is ordered or installed, especially where a falling panel or unexpected movement could cause injury or equipment damage.

Frequently asked questions

Concise answers to the questions that most often change a selection.

How is the extended length of a gas spring measured?: Measure between the defined connection reference at each end while the spring is fully extended. For eyelets and ball sockets this is normally centre to centre. For threaded ends, state whether the reference is the thread end, shoulder or another point shown on the drawing.
Is gas spring stroke the same as extended length?: No. Stroke is the distance the rod travels between the extended and compressed positions. Extended length includes the cylinder, rod, end connections and the current extension, measured between defined reference points.
Can Gemini replace a gas spring when the label is unreadable?: Often, but the application must be reviewed. Send extended and compressed lengths, rod and cylinder diameters, both fittings, mounting photographs, panel weight, hinge geometry and opening angle. Do not estimate force from physical size alone.
Should I measure a gas spring while it is installed?: Photograph and record the installation before removal, but secure the load and remove the spring when necessary to reach its true reference points. Never place yourself beneath an unsupported lid or force a pressurized spring closed by hand.

Sources and supporting documents

Published material used to check the terminology, inputs and safety guidance.

Continue with the right next step

Use the guide to collect the inputs, then move into calculation, configuration or review.

Replace a Gas Spring

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Prepare a replacement request

Gas Spring Configurator

Organize known dimensions, force, fittings and operating options.

Open the configurator

Gas Spring Calculator

Estimate force and mounting geometry for a rigid hinged door or flap.

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Connecting Parts

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