What this calculator does
G force expresses acceleration as a multiple of standard gravity, the roughly 9.8 metres per second squared that a falling object experiences at Earth's surface. Sitting still, you are already experiencing 1 g, since gravity is constantly accelerating you downward and the ground is pushing back to stop you falling through it. Anything that speeds up, slows down or changes direction faster than that adds to, or works against, that baseline.
The formula is simple division: g-force equals acceleration divided by 9.80665 metres per second squared, the internationally defined value of standard gravity. This calculator runs that conversion in both directions, from a known acceleration to its g-force, or from a target g-force back to the acceleration in metres per second squared it represents.
The formula
Standard gravity is fixed at 9.80665 m/s² by international agreement. To find g-force from an acceleration, divide the acceleration by that constant. To go the other way, from a g-force to the acceleration it represents, multiply the g-force by the same constant.
| Term | Meaning |
|---|---|
| g | G-force: acceleration expressed as a multiple of standard gravity. |
| a | Acceleration, in metres per second squared, the underlying physical quantity. |
| Standard gravity | Fixed at 9.80665 m/s², the internationally defined reference value, independent of local variations in actual gravitational acceleration. |
The inputs explained
| Field | What to enter |
|---|---|
| Calculate | Choose whether you are converting an acceleration into a g-force, or a target g-force back into an acceleration. |
| Value (m/s² if solving g-force; g if solving acceleration) | Enter the acceleration in m/s² if solving for g-force, or the g-force if solving for acceleration. |
When to use it
Reading a motorsport or track-day data logger
Lateral and braking g-force figures from a car or motorcycle's data logger are usually reported directly in g; converting a raw acceleration reading, in m/s², into the same units makes it comparable.
Checking a centrifuge or amusement ride spec
Centrifuges, roller coasters and aircraft manoeuvres are commonly rated in g, and converting a quoted or measured acceleration into that same unit lets you compare it against a published limit or a previous ride.
Working backwards from a target g-force
Given a maximum g-force a person, package or piece of equipment is rated to withstand, converting that limit into an acceleration in m/s² turns it into a number that fits directly into a separate motion or braking calculation.
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.
What g-force does a range of accelerations represent?
A range of accelerations in m/s², converted to their g-force equivalent.
| Acceleration | G-force |
|---|---|
| 1 m/s² | 0.102 g |
| 5 m/s² | 0.510 g |
| 9.8 m/s² | 0.999 g |
| 20 m/s² | 2.039 g |
| 29.4 m/s² | 2.998 g |
| 50 m/s² | 5.099 g |
What acceleration does a range of g-forces represent?
A range of g-force values, converted back to acceleration in m/s².
Questions
Is g-force the same everywhere on Earth?
Actual gravitational acceleration varies very slightly by location and altitude, but g-force calculations use the fixed, internationally defined value of 9.80665 m/s², so results are consistent regardless of where they are applied.
Why do I feel g-force when a car brakes, not just when it accelerates forward?
G-force applies to any acceleration, and braking is a (negative) acceleration in the direction of travel just as speeding up is. Cornering also produces g-force, directed sideways, because changing direction at speed is itself a form of acceleration even at constant speed.
What g-force can a human body tolerate?
It depends heavily on direction, duration and training: momentary g-forces well above 1 g are common and harmless (a hard car brake, a rollercoaster drop), while sustained high g, particularly for more than a few seconds, needs training and equipment to tolerate safely. This calculator converts the numbers; it does not assess safety.
How is g-force from circular motion, like cornering, calculated?
Centripetal acceleration in circular motion is speed squared divided by radius (v²/r). Working that out gives an acceleration in m/s², which can then be converted into g-force the same way as any other acceleration figure.
For acceleration alongside braking and stopping distance rather than g-force alone, see the acceleration and stopping distance calculator. For projectile motion under standard gravity, see the projectile motion calculator.