Have you ever been Minecraft and gotten in a tough situation, where you wouldn't know if you'd die from a jump or not?
If you answered yes, here is a solution!
If you answered no, here is a cool mod still anyways.
Video coming soon...
Just like you would install any other Forge mod for 1.8.9.
You can open the fall damage calculation GUI with a keybind. So go to your keybind settings, and under "gameplay" you should find the fall damage calculator keybind.