Sizing Gas Struts Correctly — Calculating Force in Newtons

January 8, 2026

Gas struts (also technically known as gas springs) hold upward-opening furniture flaps securely in position and control the closing motion. The required extension force is specified in Newtons (N). It is calculated primarily from the weight of the front, the flap height, and the leverage arm. As a technical rule of thumb: 10 N of force is required per kilogram of flap weight, multiplied by a leverage factor resulting from the cabinet geometry.

Fundamentals of Gas Spring Calculation

Correct sizing of fittings is crucial in cabinet making for the durability of the construction. An undersized gas spring cannot hold the flap open, leading to injury risks. If the force in Newtons is chosen too high, however, the cabinet can barely be closed, and the enormous leverage forces can tear the hinges out of the chipboard.

Acting like an invisible muscle inside the cabinet carcass, the strut takes over lifting and holding the load. The mechanism is based on a cylinder filled with nitrogen under high pressure. When closing the flap, the piston rod retracts and compresses the gas further. When opening, the gas expands and pushes the piston rod out.

This guide is aimed at installers and joiners who need to calculate and fit gas struts accurately for overhead cabinets, chests, or flap furniture. The time required for calculation and measuring the mounting points is approximately 15 to 20 minutes per cabinet.

Required Tools and Materials

For accurate determination of values and subsequent installation, you will need the following tools:

Kitchen scales or digital luggage scales (for exact weight determination of the front)
Folding rule or tape measure (for length specifications in mm)
Pocket calculator
Cordless screwdriver with matching bits (usually PZ or TX)
Chipboard screws (typically 3.5 mm or 4 mm diameter, countersunk head)
Bradawl or wood drill bit (3 mm) for pre-drilling mounting points

Step-by-Step Guide: Calculating Gas Springs for Furniture

Calculating the extension force requires accurate measurements. Estimations generally lead to malfunctioning flap mechanisms.

1. Determine Exact Flap Weight

The weight of the front is the most important variable. Weigh the flap in a disassembled state. If the front is not yet cut to size, you can calculate the weight using the specific material weight.

Typical reference values for panel materials (at 19 mm thickness):

MDF (Medium-Density Fibreboard): approx. 14 kg per square metre
Chipboard (melamine-faced): approx. 13 kg per square metre
Solid wood (oak/beech): approx. 15 kg per square metre

Always add the weight of the furniture handles. A solid bar handle made of stainless steel can easily weigh 200 to 400 grams and shifts the centre of gravity of the flap drastically downwards, which extends the leverage arm.

2. Measure Flap Height

Measure the exact height of the front in mm. The width of the flap is physically irrelevant for calculating the force in Newtons, as the weight is already derived from the total surface area. The width is only decisive for determining whether two struts must be installed (which is mandatory from a width of 400 mm to prevent warping of the front).

3. Apply the Newton Formula

In hardware technology, a simplified but very precise formula has become standard for conventional furniture flaps (opening angle 90° to 110°).

The formula is: (Flap weight in kg x Flap height in mm) / 18 = Required total force in Newtons

Calculation example: An MDF flap weighs exactly 3.5 kg including handle. The height of the flap is 400 mm. (3.5 kg x 400 mm) / 18 = 77.7 N.

Since two struts (left and right in the carcass) are always fitted from a width of 400 mm upwards, divide this value by two: 77.7 N / 2 = 38.8 N per strut.

4. Select the Right Strut

Gas springs are produced in standardised force ratings, typically in 50 N, 60 N, 80 N, 100 N, 120 N, and 150 N. In the calculation example above, you need just under 39 N per side. You round up to the next higher standard rating and choose two struts with 50 N each.

For large chests or fronts made of thick solid wood, the standard range is often insufficient. In these cases, Gas Struts for Heavy Flaps must be used, which can deliver forces from 200 N up to 450 N and more.

5. Consider Stroke and Installation Length

Besides force, the stroke is crucial. The stroke refers to the travel distance of the piston rod in mm. The total length of the strut when fully extended (measured from ball joint to ball joint) must match the internal depth and height of the carcass. A typical strut for kitchen wall units has an extended length of approx. 250 mm to 270 mm and a stroke of about 90 mm.

6. Visual Matching with the Furniture

Because the mechanism is visible when opening the cabinet, the cylinder colour should match the interior finish. For light interiors or white carcasses, Gas Struts White are ideal. In modern, dark industrial-style kitchens, Gas Struts Black blend discreetly into the overall aesthetic. For classic wood decors or technical settings, Gas Struts Silver are the standard choice.

Typical Mistakes in Selection and Installation

When designing flap cabinets, technical misunderstandings frequently arise that impair functionality.

Confusion with Furniture Dampers A gas strut is an active lifting and holding component. It must never be confused with a furniture damper (also called a soft-close buffer). A soft-close damper merely brakes the closing speed of a door, but creates no holding force.

Incorrect Hinge Selection The gas spring does not replace the function of the hinge. The flap must still be attached to the carcass using concealed cup hinges. Ensure that the opening angle of the hinges (typically 95° or 110°) matches the geometry of the strut. Whether you use a hinge for a full overlay or an inset application does not change the Newton calculation, but shifts the mounting point of the brackets by the thickness of the side panel (usually 16 mm or 18 mm).

Single-Sided Installation To cut costs, often only one strut is fitted on one side. On wide flaps, this inevitably causes the material to twist. Reveal gaps will no longer align, and hinges will wear unevenly. For front widths of 400 mm and above, always install two struts, each sized to half the total Newton requirement.

Incorrect Cylinder Orientation A common technical mistake during fitting is the wrong installation orientation. The thick body (the cylinder) should point upwards when closed, and the thin piston rod downwards. This ensures that internal lubricant continuously coats the piston rod seals, preventing drying out and maximising service life.

FAQ – Frequently Asked Questions about Sizing

Can I fit a stronger gas spring just to be on the safe side? No. If you fit a 150 N strut on a light 2 kg flap, for example, the unit can only be closed with excessive force. In the worst case, the chipboard screws will be ripped out of their fixing points due to leverage. The force must be matched precisely to the weight.

How do I find the correct mounting points inside the carcass? The exact dimensions for pilot holes depend on the manufacturer and the overall length of the strut. The fittings usually include a technical datasheet with dimensions in mm. The upper fixing point on the flap is typically located in the lower third of the front height, while the fixing point inside the carcass is set back according to the desired opening geometry (e.g. 90°). Some systems utilise the System 32 hole pattern in the carcass.

What happens if the gas spring loses force over time? Gas springs are wear items. Over the years, microscopic amounts of nitrogen can escape past the seals, reducing the holding force in Newtons. The flap will then fail to stay in its fully open position. In this case, the strut cannot be repaired or refilled; it must be replaced with a component of identical length and the same Newton rating. Replacement is usually tool-free by releasing a small spring clip on the ball joint.