What this calculator does
G-force expresses acceleration as a multiple of gravity, which makes it far easier to judge than raw metres per second squared. One g is what you feel standing still; anything above that is felt as extra weight.
It is used wherever human tolerance matters, because the body responds to acceleration in proportion to gravity regardless of the vehicle involved. A few g is uncomfortable, and sustained high values cause loss of consciousness.
The formula
Subtract the initial velocity from the final one, divide by the time, then divide by standard gravity of 9.80665 m/s² to express the result in g.
| Term | Meaning |
|---|---|
| g | Standard gravity, 9.80665 m/s². One g is the acceleration of free fall at Earth's surface. |
| Sustained versus instantaneous | The body tolerates brief high accelerations far better than prolonged ones. |
| Linear acceleration | Acceleration along a straight line, as distinct from the centripetal acceleration of cornering. |
The inputs explained
| Field | What to enter |
|---|---|
| Initial velocity (m/s) | The initial velocity in metres per second. |
| Final velocity (m/s) | The final velocity in metres per second. |
| Time interval (s) | The time over which the change happens, in seconds. |
When to use it
Comparing vehicle acceleration
A quoted zero to hundred time converts into a g figure that is easier to compare across very different vehicles.
Assessing an impact
Crash severity is usually described in g, since that is what relates to human tolerance.
Understanding a launch profile
Rocket launches are constrained by the g-loading crew and cargo can withstand.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How does acceleration time change the g-force?
The same change in speed achieved over different times.
| Time taken | G-force | Linear acceleration |
|---|---|---|
| 1 s | 2.855 g | 28.000 m/s² |
| 3 s | 0.952 g | 9.333 m/s² |
| 6 s | 0.476 g | 4.667 m/s² |
| 10 s | 0.286 g | 2.800 m/s² |
Questions
What does 1 g feel like?
Exactly what you feel sitting still, since gravity already accelerates you at that rate. Accelerating horizontally at 1 g adds a sideways force equal to your own weight.
How much can a person tolerate?
It depends on direction and duration. A few g sustained is survivable for trained people in the right posture, while brief impacts of tens of g can be survived with proper restraint. Sustained high g toward the head causes loss of consciousness.
Is braking g-force different from accelerating?
Physically no, only the direction differs. A car typically brakes harder than it accelerates, so deceleration figures are usually the larger of the two.
Does cornering count?
Yes, though this calculator handles straight-line changes only. Cornering produces centripetal acceleration, which is also expressed in g and depends on speed squared over the corner radius.
For stopping distances at those rates, see the acceleration and stopping distance calculator. For the force involved, see the force, mass and acceleration calculator.