# Acceleration

Get the acceleration value (milli g-force) in one of three dimensions, or the combined force in all directions (x, y, and z).

Find the acceleration of the micro:bit (how fast it is speeding up or slowing down).

``input.acceleration(Dimension.X);``

You measure acceleration with the milli-g, which is 1/1000 of a g. A g is as much acceleration as you get from Earth’s gravity.

Watch this video to learn how the accelerometer on the micro:bit works:

## Parameters

• dimension: the direction you are checking for acceleration, or the total strength of force.

`x`: acceleration in the left and right direction.
`y`: acceleration in the forward and backward direction.
`z`: acceleration in the up and down direction.
`strength`: the resulting strength of acceleration from all three dimensions (directions).

Forces in space

Since we don’t live on a flat world, forces happen in three dimensional space. If the movement of an object isn’t exactly in the direction of one axis, we need a way to calculate its acceleration from the values measured for all the axes together.

If you put your micro:bit on a level table and push it diagonally, you have an acceleration in two dimensions. You can find the acceleration in that direction just like how you calculate the long side of a triangle using the two shorter sides (X and Y):

`strength2D = Math.sqrt((accelX * accelX) + (accelY * accelY))`

If you decide to lift your micro:bit off the table, then you’ve just added another dimension, so insert the acceleration value for the Z axis into the equation:

`strength3D = Math.sqrt((accelX * accelX) + (accelY * accelY) + (accelZ * accelZ))`

This calculation is called the Euclidean norm of acceleration.

## Returns

• a number that means the amount of acceleration. When the micro:bit is lying flat on a surface with the screen pointing up, `x` is `0`, `y` is `0`, `z` is `-1023`, and `strength` is `1023`.

## Example: bar chart

This example shows the acceleration of the micro:bit with a bar graph.

``````basic.forever(() => {
led.plotBarGraph(input.acceleration(Dimension.X), 1023)
})``````

### Example: quake meter

Every 5 seconds, with the micro:bit facing upward on a flat surface, show how much the earth is shaking (if at all).

``````basic.forever(() => {
basic.showNumber(input.acceleration(Dimension.Strength))
basic.pause(5000)
})``````