There's a thing called terminal velocity, which is the point at which air resistance cancels out the effect of gravity - put simply, it's the maximum speed an object can reach while it's falling to earth. A quick google puts the terminal velocity of a skydiver with limbs spread out at 50 m/s and it takes around 15 seconds to reach that speed. According to
this online acceleration calculator the distance needed to achieve that would be around 374 meters. You can probably calculate how fast you'd be going after 50 meters, but given there are numerous stories of people surviving even falls from planes, I wouldn't recommend a 50 meter jump as a method.