80N or 100N Gas Struts? Guide for Medium-Weight Cupboard Flaps
Choosing between an 80 N and a 100 N gas strut depends on the exact weight of the cupboard flap as well as the leverage effect: 80 N of holding force corresponds to around 8 kg at the mounting point, whilst 100 N is designed for approximately 10 kg.
Building or repairing upward-opening wall units requires precisely matched fittings. A cupboard flap that does not stay open on its own is just as disruptive in daily use as a flap that requires significant force to pull shut. The core component of this mechanism is the gas strut. For medium-weight flaps made of engineered wood, versions with 80 N and 100 N have established themselves as standard. This guide provides the technical criteria to determine the exact rating for your construction.
The Mechanics Behind the Gas Strut
A gas strut consists of a cylinder and a piston rod. Inside the cylinder is compressed nitrogen gas. When closing the flap, the piston rod is pushed into the cylinder, compressing the gas further. When opening, the gas expands and pushes the piston out. This force assists in lifting the flap and holds it open in the end position.
Important for technical planning: Force is measured in Newtons (N). Because the strut is generally mounted very close to the hinge, a strong leverage effect is created. A flap weighing 3 kg on the scales often requires a spring force significantly higher than 30 N due to this leverage.
When planning new gas struts for a project or replacing defective components, the parameters must match the door size and material weight precisely.
Key Selection Criteria for Flap Fittings
When selecting the right fittings, hard facts matter. The assembly must reliably support the weight of the front without tearing out the hinges at the top edge.
1. Extension Force (Newtons)
The force rating is usually printed directly on the cylinder. The values 80 N and 100 N are amongst the most common ratings in furniture making. 80 N generates an extension force of approximately 8 kg, whilst 100 N pushes with about 10 kg. However, because this force is applied along a short lever arm near the pivot point, this does not mean a 100 N strut will lift a 10 kg door. Due to the leverage effect, the actual load capacity of the cupboard door is considerably lower.
2. Dimensions and Stroke
The total length of the strut in the fully extended state (from ball joint to ball joint) for standard kitchen and living room cabinets is usually in the range of 245 mm - 275 mm. The stroke—the distance travelled by the piston rod—is typically 90 mm. These dimensions determine the angle at which the flap opens (commonly 75°, 90°, or 110°).
3. Material and Design
The cylinder is usually manufactured from steel and painted. The choice of finish depends on the cabinet interior. For white or light-coloured cabinets, gas struts silver are frequently used, whereas in dark wood decors or anthracite-coloured carcases, gas struts black blend discreetly into the background.
80 N or 100 N: Which Strut for Which Application?
The choice between 80 N and 100 N is based on the height and weight of the flap. The total weight comprises the panel material (e.g. chipboard, MDF, or solid wood) and the attached handle.
An oversized strut on a light flap behaves like a lorry shock absorber on a small car—the mechanism jams, and the door can barely be pulled down without placing immense strain on the hinges. If the strut is too weak, the flap will sag.
Guidelines for Using 80 N
The 80 N variant is ideal for small to medium-sized flaps made from standard-weight panels.
- Material: Melamine-faced chipboard (16 mm or 18 mm).
- Flap height: 300 mm - 400 mm.
- Flap width: 600 mm - 800 mm.
- Front weight: approx. 2.5 kg - 3.5 kg.
- Configuration: For this weight, two 80 N struts installed in parallel are generally used.
Guidelines for Using 100 N
The 100 N version is required for heavier materials or taller fronts, as the centre of gravity of the flap sits further outwards and creates greater leverage.
- Material: Heavy MDF, lacquered fronts, solid wood, or flaps with large glass inserts.
- Flap height: 400 mm - 500 mm.
- Flap width: 800 mm - 1000 mm.
- Front weight: approx. 3.5 kg - 5.0 kg.
- Configuration: Here, too, installing a pair of two 100 N struts is the standard technical practice.
Note: For wide flaps (from 600 mm), it is always recommended to fit two struts per compartment. Fitting only a single strong strut on one side causes the door to twist when closing.
Distinction from Other Fittings
A frequent error during planning is confusing terminology. A gas strut is an opening aid. It actively pushes the flap upwards. It must not be confused with a dedicated door damper. A door damper (soft close) has no opening force; it merely cushions the momentum of a closing door.
Likewise, gas struts usually work in combination with standard hinges. If the flaps are meant to brake smoothly on closing, concealed hinges / cabinet hinges with damping (Soft Close) must also be installed on the top edge of the carcase. The gas strut holds the door open, whilst the soft-close hinge catches it softly over the final few centimetres of manual closure.
Installation Notes
Replacing or installing flap fittings requires precise measurement. Even a deviation of a few millimetres at the mounting point will drastically alter the opening angle.
- Attach mounting plates: The struts are supplied with two separate plates—one for the carcase side and one for the inside of the flap. These are secured with wood screws (typically 3.5 mm in diameter, with the length matched to panel thickness, e.g. 16 mm). A PZ drive (Pozidriv) provides the best grip for a cordless driver.
- Maintain spacing: For a 90° opening angle, the drill hole on the carcase side is usually located roughly 250 mm from the internal top edge. On the flap, the bracket is positioned at a distance of approximately 90 mm from the hinge. Exact millimetre measurements vary by manufacturer and must be taken from the enclosed data sheet.
- Observe installation orientation: The thicker side (the cylinder) should point upwards when closed, with the thinner piston rod pointing downwards. This ensures that the internal lubricant keeps the seals on the piston rod moist, prolonging service life.
- Snap into place: Once the mounting brackets are screwed down, simply push the strut onto the ball heads of the brackets until it audibly clicks into position.
Frequently Asked Questions (FAQ)
Can I replace a defective 80 N strut with a 100 N strut? No, unless the flap was demonstrably too heavy before and dropped under its own weight. Replacing 80 N with 100 N significantly increases resistance when closing. In the worst case, the excessive pressure will tear the hinges out of the chipboard. Always replace defective struts with models of the exact same Newton rating.
How do I find out how many Newtons my old strut has? The cylinder of the old strut usually has a code printed on it. Look for number sequences such as "80N", "0080N", "100N", or "0100N". These indicate the exact extension force.
How do I measure the length of a gas strut correctly? The specified length always refers to the fully extended state. Do not measure the absolute overall length, but rather the distance from the centre of one ball joint to the centre of the other ball joint (hole centre distance).
Do I really need to install two struts on a small flap? Yes, for flaps with a width of around 400 mm or more, installing struts on both sides is essential. If only a single flap stay is fitted to one side, the force acts asymmetrically. Over time, the flap will warp, fail to close flush, and cause uneven wear on the concealed hinges.
Can gas struts be repaired if they lose force? No. These are closed, pressurised systems. If the gas escapes over the years through micro-leaks in the seal, the strut loses its holding force. In this case, the component must be replaced entirely. Opening the cylinder is dangerous and technically not possible.
Suitable Categories for Your Project
To find the correct hardware for your furniture assembly or repair, navigate directly to the relevant technical categories:
- Overview of all strengths: Gas struts
- For light-coloured carcase interiors: Gas struts silver
- For dark furniture designs: Gas struts black
- Complete mechanisms for wall units: Flap fittings
- Mechanical alternatives without gas: Flap stays
- Hinges for top-hung applications: Concealed hinges / cabinet hinges with damping (Soft Close)