Newton (N) in Gas Struts: Calculating and Understanding Spring Force
The unit of measurement Newton (N) indicates the exact spring force with which a gas strut pushes a furniture front upwards and keeps it open. To select the correct fitting, the flap weight including the handle and the flap height must be calculated, as a strut that is too weak will not hold the front up, while one that is too strong makes closing difficult.
What exactly is the spring force (Newton) in gas struts?
A gas strut consists of a cylinder filled with nitrogen under high pressure and a movable piston rod. The rating in Newtons defines the extension force of this rod. In furniture construction, these components work like a pneumatic muscle within the cabinet carcase: they act as an energy store for upward-opening fronts, typically found on wall units in the kitchen or bathroom.
Important for installation practice: A gas spring must not be confused with a simple furniture damper (soft-close buffer). Whilst a soft-close damper merely slows down the closing of a door, the gas spring actively lifts the weight of the front and holds it securely in the open position.
Calculating Newtons (N): The formula for furniture making
To determine the required spring force, simply weighing the furniture front is not enough. The leverage effect of the flap plays a crucial role. The following parameters are strictly required for the calculation:
- Flap weight: The dead weight of the front in kg, strictly including the fitted furniture handle.
- Flap height: The vertical dimension from the hinge axis on the top panel to the bottom edge of the front in mm.
As a physical rule of thumb: 1 kg of weight corresponds to a gravitational force of around 10 N. Due to the leverage effect on standard wall units, this value must be adjusted in practice.
A typical calculation example for joiners: If a front made of MDF weighs 3 kg in total, this corresponds to a base load of 30 N. Because flap fittings are almost always fitted in pairs on the left and right sides of the cabinet carcase to prevent warping, the required holding force is shared. For a standard flap height of 300 mm to 400 mm, one generally selects two struts rated at 50 N or 60 N each for this weight in order to compensate for the lever travel and ensure smooth opening.
Dimensions, standards, and typical values
Standardised spring forces have become established in the hardware trade, ranging from light decorative fronts to heavy, solid flaps depending on the application. Common increments are:
- 50 N to 60 N: For very light, small fronts (e.g. microwave flaps).
- 80 N to 100 N: The standard for conventional kitchen wall units made of melamine-coated chipboard.
- 120 N to 150 N: For large or heavy fronts (e.g. made of solid wood or with mirrored glass).
For extremely wide, tall, or thick fronts, special gas struts for heavy flaps are used, which handle forces well beyond 150 N.
Alongside the force in Newtons, the installation dimension is decisive. Standard gas struts for furniture have an overall extended length of 250 mm to 270 mm. The stroke length – the distance the piston rod retracts into the cylinder – is typically 90 mm.
Application, selection, and installation
Fitting the struts is usually carried out via a clip-on mechanism onto pre-screwed mounting brackets (carcase and front mountings). When choosing, alongside the correct Newton rating, the appearance of the cabinet interior should also be taken into account. For dark cabinet interiors, gas struts in black are ideal, whilst white carcases are best suited to gas struts in white or classic gas struts in silver to maintain a consistent look inside.
Related terms
- Concealed hinge: A concealed hinge mounted on the top panel alongside the strut on standard flaps. Flap installations usually use hinges with an opening angle of 95° or 110°.
- Flap stay: A mechanical fitting without gas pressure. Flap stays hold the front open using mechanical friction or a ratchet mechanism, and their holding force can often be adjusted via an Allen screw.