How to Adjust Monitor Brightness on Ubuntu

Controlling your monitor’s brightness on Ubuntu can help reduce eye strain and save battery life. This guide will show you how to check and change your monitor’s brightness using both built-in system files and the brightnessctl tool.

Checking Current Brightness

To see your current monitor brightness value, run:

cat /sys/class/backlight/*/brightness

This command outputs a number representing the current brightness level. To find out the maximum possible brightness, use:

cat /sys/class/backlight/*/max_brightness

You can calculate the current brightness as a percentage with:

current=$(cat /sys/class/backlight/*/brightness)
max=$(cat /sys/class/backlight/*/max_brightness)
echo $(( 100 * current / max ))%

Example output:

40
100
40%

Changing Brightness Manually

To set the brightness to a specific value, write a number (e.g., 0 or 100) to the brightness file. You need sudo for this:

echo 50 | sudo tee /sys/class/backlight/*/brightness

If you want to set the brightness by percentage, calculate the value based on the maximum brightness.

Using brightnessctl to Control Brightness

The brightnessctl tool provides a simpler way to manage brightness.

Install brightnessctl

sudo apt-get install brightnessctl

Check Current Brightness

brightnessctl info

Expected output:

Device 'amdgpu_bl1' of class 'backlight':
	Current brightness: 255 (100%)
	Max brightness: 255

This command displays information about your current brightness level and the maximum brightness supported by your monitor.

Set Brightness by Value or Percentage

To set a specific value:

brightnessctl set 10   # Set brightness to 10 (about 4%)

Expected output:

Updated device 'amdgpu_bl1':
Device 'amdgpu_bl1' of class 'backlight':
	Current brightness: 10 (4%)
	Max brightness: 255

To set by percentage:

brightnessctl set 10%

Expected output:

Updated device 'amdgpu_bl1':
Device 'amdgpu_bl1' of class 'backlight':
	Current brightness: 26 (10%)
	Max brightness: 255

By following these steps, you can easily check and adjust your monitor’s brightness on Ubuntu, making your screen more comfortable for your eyes and your workflow.