G Force Calculator

How to Use the G Force Calculator

1. Choose speed change, turn or acceleration.
2. Enter the start speed.
3. Enter the end speed and pick the unit.
4. Enter the time in seconds.
5. Read the g-force, the acceleration and the combined load.

Choose how you want to describe the motion. Speed change takes a start speed, an end speed and the time between them, which is ideal for car acceleration and braking figures such as 0 to 100 km/h or 60 to 0 mph. Turn calculates the sideways g-force in a curve from the speed and the radius of the turn. Acceleration converts a value you already know in m/s² or ft/s².

The result shows the g-force, the acceleration in metric and imperial units, the direction, and the combined load you would feel with Earth’s gravity added at right angles. That last figure is what a driver or passenger actually experiences on level ground.

G-Force Formulas

One g is the acceleration of standard gravity, 9.80665 m/s², or about 32.174 ft/s². An acceleration of 2 g pushes on you with twice your body weight. Speeds must be in meters per second for the formulas, so the calculator converts km/h, mph, ft/s and knots for you.

Worked Examples

• Car launch: 0 to 100 km/h in 3.0 s. 100 km/h = 27.7778 m/s, so a = 27.7778 ÷ 3 = 9.25926 m/s² and G = 9.25926 ÷ 9.80665 = 0.944 g. Combined with gravity, the seat pushes on the driver with about 1.375 g.
• Hard braking: 60 mph to 0 in 2.5 s. 60 mph = 26.8224 m/s, so a = −10.729 m/s² and the deceleration is 1.094 g.
• Turn: 50 km/h (13.8889 m/s) around a 20 m radius curve gives a = 13.8889² ÷ 20 = 9.645 m/s², which is 0.984 g sideways.

Speeds in the turn formula must be converted to meters per second, and the radius to meters, before dividing.

Reference Accelerations

All rows are calculated directly from the formulas above. Tire grip on dry pavement usually limits ordinary cars to roughly 1 g of braking or cornering, which is why the turning example is close to the edge.

Direction Matters

G-force is a vector. Forward acceleration presses you back into the seat, braking pushes you forward against the belt, and turning pushes you outward. Vertical accelerations combine directly with gravity: a lift accelerating upward at 0.2 g makes you feel 1.2 g, and one accelerating downward at 0.2 g makes you feel 0.8 g. The combined figure here assumes the acceleration is horizontal.

Converting Between Units

To turn a speed change into g-force by hand, first convert the speeds to meters per second: divide km/h by 3.6, or multiply mph by 0.44704. Divide the change in speed by the time in seconds to get m/s², then divide by 9.80665. In imperial units, use feet per second and divide by 32.174 instead. A useful shortcut: going from 0 to 100 km/h takes about 2.83 seconds at an average of exactly 1 g, and 0 to 60 mph takes about 2.74 seconds. Anything quicker than that means the average acceleration was above 1 g.

Limits

• The speed change method gives the average acceleration over the time. Peak values during the event are usually higher.
• The turn formula assumes a constant speed on a circular path.
• Human tolerance depends strongly on direction and duration, so this tool reports the physics only. Standard gravity follows the value listed by NIST.

Frequently asked questions