2 million to 1
http://www.mythweb.com/teachers/win/odds...

I don't know the ratio, but I know it's rare to be killed falling out of bed! Of course it does happen occasionally - maybe if you were sleeping in the top bunk, and you landed on your head and broke your neck! Or if you lived in a house boat, and the boat capsized while you were sleeping and you drowned! Or if you lived in a trailor park and there was a tornado, and it picked up your trailor, spinning you out of bed and slamming you around breaking every bone in your body! Or, if you slept in a loft, and fell out of bed landing two storey's below impaled on a fireplace poker! Or if your house was on the San Andreas fault, and there was a major earthquake in the middle of the night, and you fell out of bed while your house was being swallowed up by a gaping crevice in the earth's surface. Or if a car hit your house ramming into your bedroom, knocking you out of bed and pinning you up against the wall with a bumber up your butt! I'm done!

99.9%

http://www.brainofbrian.com/facts-statis...

It depends how you fall. If you fall with your head directly hitting the ground and if certain nerve of the skull gets damaged then it can be life threatening.

well scientifically its 35000:1