How to Calculate Torque Hinge Requirements | Formula + Examples

Specifying a torque hinge starts with one number: the holding torque your application needs. Get it right, and the panel stays exactly where the user leaves it for the life of the product. Get it wrong, and the panel either drifts shut under its own weight or feels stiff and awkward to move. This guide shows you how to calculate the required torque in five steps, with three worked examples and the safety factors that experienced engineers apply.

This article is part of our complete torque hinges guide. If you need a refresher on what torque hinges are and how they work, start with our overview of what a torque hinge is.

The Physics: Why Torque, Not Just Weight

A common mistake is to size a hinge by panel weight alone. Weight matters, but what the hinge actually resists is torque — the rotational force created by that weight acting at a distance from the pivot. A light panel mounted far from the hinge axis can demand more torque than a heavy panel mounted close to it.

Torque is the product of force and distance. The force is the panel’s weight acting through gravity. The distance — called the moment arm — is measured from the hinge’s rotation axis to the panel’s centre of gravity, measured horizontally when the panel is in its worst-case (usually horizontal) position. The further the centre of gravity sits from the axis, the more torque the hinge must resist to hold position.

Units: N·m and kgf·cm

Torque is most commonly specified in newton-metres (N·m). Some catalogs use kilogram-force centimetres (kgf·cm), particularly in Asia. The conversion is straightforward: 1 N·m equals approximately 10.2 kgf·cm. HSP catalog torque values are specified in N·m, with models available from 0.1 N·m for mini hinges up to 25 N·m for heavy-duty adjustable torque hinges.

The Formula, Step by Step

Here is the full calculation process. Work through it once with your own numbers and torque selection becomes a repeatable, defensible engineering decision rather than a guess.

1. Measure the panel weight (W). Weigh the panel, lid, or screen the hinge will carry, including anything mounted on it — a display, cables, accessories, or a cover. Use the heaviest realistic configuration. Result in kilograms.
2. Find the centre of gravity distance (d). Measure horizontally from the hinge rotation axis to the panel’s centre of gravity, in the position where gravity creates the most torque (usually when the panel is horizontal). For a uniform flat panel, the centre of gravity is at its geometric centre. Result in metres.
3. Calculate the static holding torque (T). Multiply: T = W × 9.81 × d. The 9.81 converts mass to gravitational force. Result in newton-metres.
4. Apply a safety factor. Multiply the static torque by 1.5 for normal applications, or by 2 for high-cycle, high-vibration, or safety-critical applications. This accounts for torque retention loss over the hinge’s life and real-world load variation.
5. Divide across multiple hinges if used. If the panel uses two hinges, each carries roughly half the load — divide the required torque per hinge accordingly. Most panels use at least two hinges for stability.

Three Worked Examples

The formula is clearest when applied to real cases. Here are three across different load ranges and industries.

Example 1 — Laptop or Tablet Screen (light load)

A foldable display screen weighs 0.4 kg, with its centre of gravity 150 mm (0.15 m) from the hinge axis when open.

• Static torque: 0.4 × 9.81 × 0.15 = 0.59 N·m
• With 1.5× safety factor: 0.59 × 1.5 = 0.88 N·m
• Across two hinges: roughly 0.45 N·m per hinge
• Selection: a mini or constant torque hinge in the 0.5–1.0 N·m range per hinge. This sits well within HSP’s mini torque hinge range, which offers resolution as fine as 0.1 N·m.

Example 2 — Industrial HMI Control Panel (medium load)

An operator control panel weighs 3 kg, with its centre of gravity 200 mm (0.2 m) from the hinge axis. It is opened and closed many times per shift, so it is a high-cycle application.

• Static torque: 3 × 9.81 × 0.2 = 5.89 N·m
• With 2× safety factor (high-cycle): 5.89 × 2 = 11.8 N·m
• Across two hinges: roughly 5.9 N·m per hinge
• Selection: an adjustable torque hinge rated around 5–6 N·m per hinge. An adjustable torque hinge is the right call here — it lets the operator fine-tune the feel after installation as the panel load or preference changes.

Example 3 — Self-Service Kiosk Rotating Display (heavier load)

A kiosk display assembly weighs 5 kg, with its centre of gravity 300 mm (0.3 m) from the rotation axis. It rotates for customer and operator viewing and must hold any angle.

• Static torque: 5 × 9.81 × 0.3 = 14.7 N·m
• With 1.5× safety factor: 14.7 × 1.5 = 22.1 N·m
• Selection: at this level the requirement approaches the top of the standard torque range, so distributing the load across two hinges (about 11 N·m each) or specifying a custom high-torque unit is the practical route. A swivel torque hinge suits the rotating motion, and HSP can develop custom torque values up to 25 N·m for applications at this end of the range.

Choosing the Right Safety Factor

The safety factor is not padding — it accounts for real engineering effects that erode holding torque over time and operating conditions. Choosing it well is the difference between a hinge that holds for the product’s life and one that drifts after a year.

Common Mistakes to Avoid

• Sizing by weight, ignoring distance. The moment arm matters as much as the weight. A light panel on a long arm can need more torque than a heavy panel mounted close in.
• Forgetting the safety factor. Sizing to the exact static torque leaves no margin for the torque loss that every friction hinge experiences over its cycle life.
• Ignoring added mass. Cables, a heavier display revision, or accessories added later all increase the load. Size for the heaviest realistic configuration.
• Over-specifying torque. Too much holding torque makes the panel stiff and hard to move, and can stress the mounting points. Aim for the calculated value plus safety factor — not the highest torque available.
• Assuming one hinge. Most panels use two or more hinges. Divide the load — but also ensure each hinge alone can hold the panel if it is opened unevenly.

When to Use Multiple Hinges

Distributing load across multiple hinges is standard practice for panels above roughly 1–2 kg, or any panel wider than it is tall. Two hinges share the torque demand and improve alignment stability; three or more are used for long or heavy doors. When using multiple hinges, divide the total required torque by the number of hinges to find the per-hinge rating — but specify each hinge so it can safely hold the panel even if the load is not perfectly balanced between them.

Frequently Asked Questions