What Is Break Force? Definition, Uses, and How It’s Measured

Break force is the amount of force required to make a material, component, or connection fail—snap, tear, pull apart, or otherwise fracture. Often called “force at break,” “breaking force,” or “break load,” it’s reported in newtons (N) or pounds-force (lbf). It’s not the same as “brake force,” which refers to the force that slows or stops motion.

The core definition

In testing and engineering, break force is the peak load recorded at the instant a specimen fails under an applied load. Unlike strength (which is force per unit area), break force is a raw force value that does not account for cross-sectional area. The closest stress-based counterpart is “ultimate tensile strength,” calculated by dividing the break force by the specimen’s original cross-sectional area.

Related terms and common confusions

Because “break” and “brake” sound alike, the terms are sometimes mixed up. Break force (fail at a load) is different from brake force (decelerate a moving object). You may also see synonyms such as “force at break,” “break load,” and, in consumer contexts, “breaking strain/strength,” though strictly speaking “strength” should be expressed as stress (force divided by area).

Where you’ll encounter break force

Break force is a practical metric in many industries and everyday products. The following examples illustrate how the term is used across materials and applications.

• Materials testing: Plastics, metals, composites, and films are pulled in a tensile tester until they break; the peak force is recorded.
• Textiles and fibers: Fabrics, yarns, ropes, and webbing are tested to failure to determine safe working loads and quality consistency.
• Fishing lines and cordage: “Breaking strength” on packaging reflects the measured break force converted to stress or quoted directly as a load.
• Packaging and seals: Tamper-evident bands, blister packs, and seals are evaluated for the force required to open or tear them.
• Magnetic and mechanical attachments: “Pull-off” or “breakaway” force tells you how much load detaches a magnet, clip, or connector.
• Electrical and medical connectors: Breakaway force defines how easily a connector disengages to prevent equipment damage or patient harm.

Taken together, these use cases show that break force is both a safety benchmark and a quality metric, guiding design limits and user experience.

How break force is measured

Most measurements are performed with a universal testing machine (UTM) or calibrated force gauge, using standardized procedures so results are comparable.

1. Prepare specimens: Cut or condition samples to a defined geometry and environmental state (temperature/humidity) per the relevant standard.
2. Fixture and align: Mount the specimen in grips or fixtures that prevent slippage and align the load path to avoid bending.
3. Apply load at a controlled rate: Pull (or sometimes compress/peel) at the specified speed while the instrument records force versus displacement.
4. Capture the peak: The highest force just before failure is the break force; note the failure mode (e.g., brittle fracture, ductile necking, slippage).
5. Repeat and report: Test multiple specimens, report mean and dispersion, and include test rate, environment, grip type, and specimen details.

Control over strain rate, temperature, humidity, and specimen geometry is critical, as these factors can shift break force substantially.

Typical standards and instruments

Different materials and failure modes call for different methods. The standards below are commonly referenced for measuring force at break or closely related failure forces.

• Plastics and composites (tension): ASTM D638, ISO 527
• Thin plastic films: ASTM D882
• Textiles and fabrics: ASTM D5034 (grab), ASTM D5035 (strip), ISO 13934-1 (strip)
• Yarns/fibers: ASTM D2256, ISO 2062
• Fibre ropes: ISO 2307
• Steel wire ropes: ISO 2408 (general requirements; tensile tests reference related methods)
• Adhesion/pull-off and peel (failure force of joints): ASTM D3330 (peel), ASTM D4541 / ISO 4624 (pull-off), ASTM D1002 (single-lap shear)
• General-purpose testers: Universal testing machines with appropriate load cells; handheld digital force gauges for field checks

Referencing a recognized standard ensures consistent specimen preparation, loading rates, and reporting, allowing fair comparisons across labs and products.

Units, conversions, and a quick example

Engineers report break force as a load and may convert to stress for strength comparisons across sizes.

• Common units: newton (N), kilonewton (kN), pound-force (lbf). Conversion: 1 lbf ≈ 4.44822 N.
• From force to strength: Ultimate tensile strength = break force ÷ original cross-sectional area.
• Example: If a sample breaks at 100 N and its area is 2 mm² (2 × 10⁻⁶ m²), the strength is 100 N ÷ 2e-6 m² = 50 MPa.

This distinction—force versus stress—matters when comparing materials or components of different sizes.

Safety and engineering considerations

Real-world use rarely allows operating right at the measured break force. Engineers apply margins to account for variability and conditions.

• Design/safety factors: Working loads are often set to a fraction of the measured break force (e.g., 4:1 to 12:1 for ropes and lifting slings, depending on regulation and risk).
• Variability: Manufacturing tolerances, defects, and aging can reduce break force; batch testing helps track consistency.
• Environment: Temperature, humidity, UV exposure, chemicals, and water absorption can raise or lower break force.
• Rate effects: Many polymers and adhesives show higher break force at faster pull rates and lower values at slower rates or elevated temperatures.

Accounting for these factors helps ensure products remain safe and reliable across their service life, not just in the test lab.

Summary

Break force is the maximum load a material or component can withstand before failing, reported as a force (N or lbf). It is widely used across materials testing, textiles, cordage, packaging, and attachment systems. Measured with standardized methods on UTMs or force gauges, it underpins safety factors and product specifications. Don’t confuse it with brake force, which describes deceleration; break force is about the load that causes failure.

Are breaking strength and breaking force the same?

Force: Tensile strength measures the stress a material can handle per unit area, while break strength measures the total force required for complete failure.

What is the unit of breaking force?

Break strength is a measure of the force required to break an object. It is typically expressed in units of force per unit area, such as pounds per square inch (psi) or newtons per square meter (N/m^2).

What is break loose force?

Break-Loose Force, or initiating force, is defined as the amount of maximum force required to dislodge the plunger from its resting position in the barrel of the syringe. Glide Force, or sustaining force, is defined as the force required to maintain plunger movement once static friction has been overcome.

What do you mean by breaking force?

Braking force is the opposing force generated by a brake system to slow down or stop a moving object, such as a vehicle. It works by converting the object’s kinetic energy into heat through friction, with factors like mass, speed, and the coefficient of friction all influencing the required braking force to achieve a safe stop. 
How it works

1. Application of brakes: Opens in new tabWhen brakes are applied to a vehicle, a system (like brake pads) creates friction against moving parts. 
2. Friction and Energy Conversion: Opens in new tabThis friction creates a braking force that opposes the motion of the vehicle. The kinetic energy (energy of motion) of the vehicle is then converted into thermal energy (heat) through the friction between the brake pads and the discs or drums. 
3. Deceleration: Opens in new tabThis force causes the vehicle to decelerate (slow down), eventually bringing it to a stop. 

Factors influencing braking force

• Mass: Opens in new tabA heavier vehicle requires a greater braking force to achieve the same deceleration, as per Newton’s second law of motion (F=ma). 
• Velocity: Opens in new tabThe faster a vehicle is moving, the greater the braking force needed to stop it within a specific distance, due to higher initial kinetic energy and a larger deceleration requirement. 
• Friction: Opens in new tabThe effectiveness of the braking force is directly dependent on the friction generated between the brake components and between the tires and the road. 
• Stopping Distance: Opens in new tabBraking force is a primary factor in determining a vehicle’s stopping distance, which is the total distance required to come to a complete halt.