How Many Gs are Fatal? Understanding Lethal G-Force

G-force, or gravitational force, is a crucial measurement of acceleration that can have a significant impact on the human body. In this article, we will explore the lethal effects of G-force, the human body’s ability to tolerate it, and the factors that determine its lethality.

What is G-force?

G-force refers to the force of acceleration experienced by an object, in this case, the human body, due to gravity. One G is equivalent to the Earth’s gravity, which is approximately 9.81 meters per second squared (m/s^2). When individuals are subjected to higher G-forces, they feel heavier because their bodies have to support more weight.

The Impact of G-force on the Human Body

The effects of G-force on the human body depend on various factors, including the duration of exposure, the direction of the force, and an individual’s physical fitness. There is no universal answer to the maximum G-force a person can withstand, as it varies from person to person.

Positive G-force

Positive G-forces, also known as “eyeballs in,” are felt in the head-to-feet direction. Untrained individuals can typically endure up to 5 Gs for a short period before losing consciousness due to blood pooling in the lower extremities, away from the brain. With specialized training, some fighter pilots can withstand up to 9 Gs for brief bursts without losing consciousness. However, sustaining such high positive G-forces for extended periods can lead to severe injury or even death.

Negative G-force

Negative G-forces, also known as “eyeballs out,” are felt in the chest-to-back direction and are more dangerous than positive G-forces. When experiencing negative G-forces, blood can pool in the head, causing a condition known as “redout.” This can lead to the rupture of blood vessels in the eyes and brain, potentially resulting in vision loss or a stroke. Most people can only endure around -2 to -3 Gs before experiencing severe discomfort and potential injury.

How many Gs are Fatal

The lethality of G-force is determined by exposure versus time. The higher the G-force, the less time it takes for it to become lethal. However, there is a threshold below which G-force is not fatal, likely somewhere below 6G.

It is important to note that the direction of the G-force is a critical factor. Positive G-forces are more survivable compared to negative G-forces. Humans have survived lateral G-forces of more than 200G, albeit only for an extremely brief moment.

An G-force as extreme as 11.327 million psi is far beyond the limits that any human body could endure. This value is simply incomprehensible in terms of its destructive potential. Such a force would subject the human body to unimaginable pressures that would undoubtedly lead to immediate and catastrophic consequences.

Surviving High G-forces

Astronauts, fighter pilots, and thrill-seekers on roller coasters often experience high G-forces. Specialized training and equipment can increase an individual’s ability to withstand G-forces.

For positive G-forces, specific breathing techniques and anti-G suits allow some fighter pilots to handle up to 9 Gs for short bursts without losing consciousness. However, prolonged exposure to such high G-forces can lead to severe injury or death.

In contrast, the human body can tolerate higher G-forces if they are applied for an extremely brief duration, such as in car crashes or during ejection from an aircraft. In these situations, people have survived impacts with forces up to 100 Gs, but only for a few milliseconds.

One real-time example of a human experiencing lethal G-force was the case of Donald Campbell, a British speed record breaker. On January 4, 1967, Campbell attempted to break his own water speed record on Coniston Water in England, using his high-speed boat, the Bluebird K7.

During the attempt, tragedy struck as the Bluebird K7 crashed at a speed exceeding 300 miles per hour. The crash was the result of the boat hitting the water at a slightly nose-down angle, causing it to somersault and break apart. The impact generated an extremely high G-force, and Campbell was killed instantly.

The accident was thoroughly investigated, and it was concluded that the high speed combined with the angle of impact resulted in G-forces that were too much for the human body to withstand, leading to the tragic loss of Donald Campbell’s life. This incident serves as a somber reminder of the immense danger associated with high-speed activities and the potential lethal consequences of extreme G-forces.


In conclusion, G-force can have deadly consequences when exposure exceeds the body’s tolerance levels. Positive G-forces can be endured to a certain extent, especially with proper training, while negative G-forces pose a greater risk of injury or fatality. Understanding the limits of G-force and its effects on the human body is essential for those who encounter high acceleration forces, as it can mean the difference between life and death.

Remember, when it comes to G-forces, knowledge and preparation are crucial for survival. So, whether you’re an astronaut, a pilot, or simply an adrenaline junkie seeking thrill rides, always prioritize safety and adhere to the guidelines set forth by experts in the field. Stay informed, stay safe, and enjoy the wonders of G-forces responsibly.


  • Dr Khadija

    DPT | MS Pain Management | Intra-articular Injec Specialist | Acupuncturist | Cupping Therapist | Oncology Pain Specialist | Certified Chiropractor 🇬🇧 | Medical Writer | Author