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G-Force Calculator

Find how many g's an acceleration is, from a speed change over time, a stopping distance, a turn radius or an acceleration you already know.

Level: Grades 11–12

Printable worksheet

G-Force Calculator

Know the answer you need? Pick an input to work backward.

Inputs
Find the g-force from

Result

G-force

0.9442 g

The acceleration is 9.2593 m/s², or 0.9442 g.

Acceleration
9.2593 m/s²
Acceleration in ft/s²
30.3781 ft/s²
Direction
Speeding up

See the step-by-step solution ↓

Step-by-step solution

  1. Change the starting speed to m/s, the standard unit the formula uses (1 km/h = 0.277777777778 m/s)

    0 km/h×0.277777777778=0 m/s

  2. Change the final speed to m/s, the standard unit the formula uses (1 km/h = 0.277777777778 m/s)

    100 km/h×0.277777777778=27.777778 m/s

  3. Find the acceleration: how much the speed changed, divided by how long it took

    27.777778−03=9.259259 m/s²

  4. Divide the size of the acceleration by standard gravity (9.80665 m/s²) to see how many g it is

    9.2592599.80665=0.944182 g

Test yourself

20 quick questions built from this calculator's formula: work out results, predict what happens when an input changes, and work backward from an answer. Every answer comes with the working.

What this calculator does

Find out how many g's a launch, a hard stop or a tight turn puts on you. G-force describes acceleration (how fast speed or direction changes) by comparing it with the pull of gravity at the Earth's surface. An acceleration of 1 g is 9.80665 meters per second squared. That's the agreed value of standard gravity. A sports car launching hard might reach about 1 g. A roller coaster can briefly push riders to 4 or 5 g. Trained pilots in special suits can handle around 9 g for short periods.

Most people don't know their acceleration directly. So this calculator works from things you can measure: how quickly a speed changes, how far something takes to stop, or how fast it goes around a curve of a given radius. You can also type in an acceleration in m/s², ft/s² or g. The answer is always the size of the acceleration divided by standard gravity. You'll also see the acceleration itself and which way it points.

Where it's used

Why this math matters outside the classroom:

  • Roller coasters. Coaster designers check that a loop's radius and speed keep riders within comfortable g-forces.
  • Hard braking. A car stopping from 100 km/h in 3 seconds averages about 9.3 m/s², roughly 0.94 g.
  • Pilot training. Fighter pilots train to withstand high g in tight turns, where a = v²/r grows quickly with speed.
  • Phone sensors. Phone accelerometers report readings in g, so a phone lying flat on a table shows about 1 g.

How to use it

  1. Choose the situation: a speed change over a time, steady braking over a distance, a turn or loop, or an acceleration you already know.
  2. Enter the speeds, time, distance or radius, with their units.
  3. Read the g-force, the acceleration in m/s² and ft/s², and its direction.

What the inputs mean

Acceleration (a)
Negative values (braking) are fine; g-force uses the size of the acceleration.
Starting speed
The speed at the start. Use 0 for a standing start.
Time taken
How long the speed change takes. A 0–100 km/h time of 3 seconds is a fast road car.
Stopping distance
The distance covered from the moment braking starts until the object stops. This assumes the braking force stays the same the whole way.
Radius of the turn
The radius of the curved path (the distance from its center to the path). A tighter turn at the same speed gives a larger g-force.

Formula and method

g-force = |a| ÷ g₀, g₀ = 9.80665 m/s²
a = (v₂ − v₁) ÷ t
a = v² ÷ (2 × d)
a = v² ÷ r

Here's what the symbols mean. a is the acceleration, and |a| is its size, ignoring direction. g₀ is standard gravity. v₁ and v₂ are the starting and final speeds, and t is the time. v is the speed when braking or turning, d is the stopping distance and r is the turn radius.

Each mode finds an acceleration in m/s² first. A speed change uses the average rate of change. Steady braking from speed v to a stop over distance d comes from the motion equation v² = 2ad. A turn uses the centripetal acceleration (the pull toward the center) of circular motion, v² ÷ r.

Then the acceleration is divided by standard gravity, 9.80665 m/s², which is exact by international agreement. Speeds are converted to meters per second and distances to meters before any math. So mixed units, such as km/h and feet, are handled correctly.

Worked example

A car speeds up from a standstill to 100 km/h in 3 seconds. What g-force do the passengers feel pushing them into their seats?

  1. Convert the final speed: 100 km/h × 0.277777777778 = 27.777778 m/s.
  2. Average acceleration: (27.777778 − 0) ÷ 3 = 9.259259 m/s².
  3. G-force: 9.259259 ÷ 9.80665 = 0.944182 g.

Result: The passengers feel about 0.94 g of push from the seat back. That's on top of the normal 1 g of gravity pulling them down.

Understanding the result

This figure is the g-force from the motion you described, and nothing else. In a car, the 0.94 g push is horizontal (level with the road). It adds to the 1 g of gravity pulling you down. So the total load on your body is a little more than either one alone, about 1.37 g in this case.

For up-and-down motion, such as an elevator or the bottom of a roller coaster dip, it's different. The load you feel is the motion's g-force plus or minus 1 g, depending on direction. Pilots and riders call that total the g they pull.

Assumptions and limitations

  • Accelerations are averages. The speed changes at a steady rate over the time, and the braking force stays the same over the distance.
  • Turns are treated as parts of a circle, taken at a steady speed.
  • Standard gravity, 9.80665 m/s², counts as 1 g everywhere.
  • Peak g-forces during a launch, crash or bump can be far higher than the average shown here.
  • The result doesn't combine the motion with gravity. To find the total load you feel, add the two as vectors (taking their directions into account).
  • How much g-force a person can handle depends on direction, how long it lasts and fitness. This calculator makes no judgment about tolerance or safety.

Frequently asked questions

What is 1 g in m/s² and ft/s²?

One g is exactly 9.80665 m/s² by definition, which is about 32.174 ft/s². It's the agreed standard value of gravity at the Earth's surface.

Why is standing still counted as 1 g?

When you stand on the ground, the floor pushes up on you to stop you falling. That push is what your body senses. An accelerometer (a motion sensor) sitting still reads 1 g for the same reason. One in free fall reads 0 g.

Can g-force be negative?

This calculator reports the size of the acceleration. So the g-force is never negative, and the direction is shown separately. Pilots do use negative g for a load that pushes them up out of the seat, as at the top of an outside loop.

How many g does braking produce?

Ordinary braking is a few tenths of a g. A hard emergency stop on dry pavement in a modern car is often near 1 g. For example, stopping from 100 km/h in 40 m works out to about 0.98 g.

How this calculator is checked

Method: Kinematics (a = Δv/t, v² = 2ad, a = v²/r) divided by standard gravity g₀ = 9.80665 m/s² (CGPM 1901). The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.

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