G-Force Calculator
Select a calculation mode, enter your values, and get the g-force instantly. The linear mode finds the g experienced during any acceleration or braking event. The circular mode calculates centripetal g at a given speed and turn radius. The centrifuge mode converts RPM to relative centrifugal force (RCF). The gravity mode works out surface gravitational acceleration for any planet-sized body from its mass and radius. Unit switches, a step-by-step panel, and a real-world reference table are included.
What is g-force?
G-force (also written as g-force or simply g) is a measurement of acceleration relative to free fall. One g is defined as the standard acceleration of gravity at Earth's surface, exactly 9.80665 m/s^2. When you are sitting still on Earth you experience 1 g downward because the ground is pushing you upward with that same force. During any other acceleration, the g-force tells you how many times heavier or lighter everything feels compared with normal Earth gravity. A 3 g cornering load means every object in the car temporarily weighs three times its normal weight. In free fall or orbit you experience 0 g (weightlessness) because there is no reaction force pushing back against you.
The four calculation modes explained
Linear mode: g-force = (v1 - v0) / (t * 9.80665). Enter start speed, end speed, and the time taken. Braking gives a negative g-force. Circular mode: g-force = v^2 / (r * 9.80665). Enter the cornering speed and the turn radius. Tighter turns and higher speeds multiply g dramatically. Centrifuge mode: g-force = (2*pi*RPM/60)^2 * r / 9.80665, which simplifies to approximately RPM^2 * r_cm * 1.118 x 10^-5. Enter rotor speed and effective radius to get RCF (Relative Centrifugal Force), the standard unit used in laboratory protocols. Gravity mode: g = G*M/R^2, where G is 6.674 x 10^-11 Nm^2/kg^2. Enter planetary mass and mean radius to find surface gravity as a multiple of Earth standard.
Human tolerance and safety context
The human body tolerates g-force differently depending on direction, duration, and training. A sustained 4-5 g (chest-to-back direction) causes grey-out and eventually G-LOC (G-force induced Loss Of Consciousness) in untrained individuals; fighter pilots with G-suits and anti-G straining manoeuvres can sustain around 9 g. Short-duration spikes are less dangerous: a sneeze briefly produces around 2.9 g, and a hard car emergency stop around 0.8-1.0 g. Negative g-forces (head-down or braking) are harder to tolerate than positive ones: the redout threshold is about -2 to -3 g. Centrifuge machines in laboratory settings routinely produce thousands of g, but they act on small samples, not people.
Centrifuge RCF vs RPM - a practical note
Laboratory protocols typically specify RCF (x g) rather than RPM because the same RPM produces different forces in rotors of different sizes. Always convert to RCF using the rotor's rated radius, which is usually the maximum radius (tip of sample). The quick formula is: RCF = 1.118 x 10^-5 * r_cm * RPM^2. At 3,000 RPM with a 10 cm radius rotor, RCF = 1.118 x 10^-5 * 10 * 9,000,000 = approximately 1,006 x g. This calculator uses the exact formula via angular velocity for higher precision.
Real-world g-force reference values
| Scenario | Typical g-force | Notes |
|---|---|---|
| Standing still on Earth | 1 g | Baseline gravitational load |
| Commercial aircraft take-off | 0.3-0.5 g | Gentle forward acceleration |
| Comfortable car cornering | 0.3-0.4 g | Normal road speeds on a turn |
| Hard car braking (ABS) | 0.8-1.0 g | Full emergency stop on dry road |
| Sports car 0-100 km/h in 3 s | 0.9-1.0 g | High-performance launch |
| Formula 1 cornering | 4-6 g | High-downforce racing car |
| Roller coaster peak | 3-6 g | Varies widely by ride design |
| Ejection seat activation | 12-14 g (brief) | Lasts only milliseconds |
| Fighter jet maximum manoeuvre | 9 g | Limit with G-suit and AGSM |
| Space Shuttle launch | 3 g (peak) | Astronauts trained and suited |
| Moon surface gravity | 0.166 g | 1.62 m/s^2 |
| Mars surface gravity | 0.378 g | 3.71 m/s^2 |
| Jupiter surface gravity | 2.528 g | 24.79 m/s^2 |
Approximate g-forces for common scenarios. Negative values indicate braking/deceleration.
Frequently asked questions
How do you calculate g-force from speed and time?
Subtract the starting speed from the ending speed (in m/s) to get the change in velocity (delta v). Divide that by the duration in seconds to get acceleration in m/s^2. Then divide by 9.80665 to convert to g-force. For example, accelerating from 0 to 27.8 m/s (100 km/h) in 4 seconds gives an acceleration of 6.94 m/s^2, which equals 0.71 g.
What g-force do you feel in a roller coaster?
Typical roller coasters produce between 3 g and 6 g at peak points such as the bottom of a loop or a sharp valley. The world record rides have briefly exceeded 6 g. At the top of a loop you may feel near 0 g (momentary weightlessness) if the ride is designed that way.
What is the difference between RCF and RPM in a centrifuge?
RPM (revolutions per minute) describes how fast the rotor spins. RCF (relative centrifugal force) describes the actual force experienced by the sample, expressed as a multiple of standard gravity. Because a larger rotor radius produces more force at the same RPM, protocols specify RCF so the result is the same regardless of which centrifuge model you use. Use this calculator's centrifuge mode to convert between the two.
At what g-force do humans lose consciousness?
Untrained individuals typically begin to grey out (loss of peripheral vision) around 4-5 g when the force acts upward from feet to head (the most dangerous direction). Full G-LOC can occur above 5-6 g sustained for several seconds. With training, G-suits, and anti-G straining manoeuvres, fighter pilots can tolerate up to approximately 9 g.
How much g-force does a car feel during hard braking?
A standard road car with ABS braking on dry pavement typically decelerates at 0.8-1.0 g. High-performance cars and race cars with slick tyres can exceed 1.5 g under braking. Formula 1 cars routinely brake at 4-5 g entering slow corners.
What is the g-force on other planets?
Mars has a surface gravity of about 0.378 g (3.71 m/s^2), the Moon is 0.166 g (1.62 m/s^2), Jupiter is 2.528 g (24.79 m/s^2), and Venus is 0.904 g (8.87 m/s^2). Use the gravity mode, enter the planet's mass and mean radius, and the calculator will work out the surface g.