Bite force, or masticatory force, is the mechanical force generated by the muscles of the jaw as they close. Determining a single, definitive number for human bite force is not possible because the measurement varies significantly between individuals. The jaw’s strength is a dynamic capability influenced by multiple anatomical and physiological factors.
How Scientists Measure Bite Force
Scientists quantify human jaw strength using specialized instruments called gnathodynamometers or occlusal force transducers. These devices are placed between the teeth, typically on the molars, and record the maximum voluntary force exerted by a person. The standard units of measurement for this type of research are Newtons (N) for total force and Pounds per Square Inch (PSI) for pressure.
Force, measured in Newtons, is the total magnitude of the push, while pressure (PSI) is the force distributed over a specific surface area. For an average adult, maximum bite force on the molars ranges between 120 and 160 PSI. Peak voluntary exertion can push this upper limit to around 200 PSI in healthy individuals.
The location of the measurement significantly influences the reading because the jaw acts as a lever. Force measurements taken on the incisors, which are further from the joint, will naturally be lower than those taken on the molars, which are positioned closer to the jaw’s fulcrum. This mechanical reality means the posterior teeth are built to handle the highest pressures during the act of chewing.
Biological Factors Driving Bite Strength
The power behind the human bite originates from the coordinated contraction of the jaw-closing muscles, primarily the masseter and the temporalis. The masseter is a thick, powerful muscle that runs from the cheekbone down to the lower jaw, providing the bulk of the vertical closing force. The temporalis muscle, a fan-shaped structure on the side of the head, assists in closing the jaw and helps with its retraction.
The maximum strength an individual can produce is directly related to the thickness and cross-sectional area of the masticatory muscles. Studies confirm a positive correlation between masseter muscle thickness and a person’s occlusal force. The skeletal structure of the face, known as cranio-facial morphology, also impacts this strength. Individuals with a “short-faced” structure, characterized by a more compact jaw, exhibit stronger bite forces due to a better mechanical advantage.
Dental occlusion, which is how the upper and lower teeth align and meet, also plays a significant role in bite efficiency and strength. A greater occlusal contact area, such as that provided by the broad surfaces of the molars, allows for a more effective distribution of force. Secondary factors, including age-related muscle deterioration and overall bone density, contribute to the gradual changes in a person’s maximum bite capability over their lifetime.
Comparing Human Bite Force to the Animal Kingdom
Placing the average human bite force of 120 to 160 PSI into a broader biological context shows that our species prioritized precision and endurance over brute crushing power. Many animals evolved highly specialized and significantly stronger bites necessary for capturing and processing tough prey. The Spotted Hyena, for instance, possesses a bite force estimated to be around 1,100 PSI, which allows it to crush and consume the bones of its kills.
Reptiles and large predators demonstrate jaw strength that dwarfs human capability. The Saltwater Crocodile, an apex predator, has a bite force measured at up to 3,700 PSI. This immense force is achieved not through large jaw-opening muscles but through massive muscles engineered for a powerful, vice-like closing action. The Great White Shark also registers an estimated bite force in a similar range, with digital reconstructions suggesting it can exceed 4,000 PSI.
A gorilla, which is primarily a herbivore, exhibits a much higher bite force, estimated at 1,300 PSI, used to process tough, fibrous plant material. Anatomical differences, such as larger skull size and robust jaw musculature, explain the disparity in power. While the human jaw is optimized for a varied diet and complex speech, animal jaws are specialized tools for hunting, defense, and consuming specific types of difficult food sources.