diff --git a/fish/functions/decrease_brightness_by.fish b/fish/functions/decrease_brightness_by.fish
new file mode 100644
index 0000000..856d905
--- /dev/null
+++ b/fish/functions/decrease_brightness_by.fish
@@ -0,0 +1,5 @@
+function decrease_brightness_by --argument-names amount
+  set --local brightness (cat /sys/class/backlight/*/brightness)
+  set --local brightness_increased (math $brightness - $amount)
+  echo $brightness_increased | sudo tee /sys/class/backlight/*/brightness > /dev/null
+end