You are standing on a bridge or cliff. It's a long way down. But how high are you? Fallometer answers this question.
Select the thing you will drop, and press START when you drop it, and STOP when it hits the ground.
Fallometer will estimate how far it fell and how fast it was going when it hits the bottom.
Fallometer takes into account air friction, and your position on earth.
There is a paid version of Fall-o-meter if you do not want advertisements.