Cessna 182

Quick question, and I know that someone here will know the answer:

How much runway is needed to get a (relatively) empty 182 off the
ground? I am thinking one pilot, 45 minutes of fuel, and 1000 MSL.
Grass.
I once saw an Iowa State Trooper land a State 182 on concrete, little
wind, in less than 500 feet. Just wondering what the machine will do
on takeoff when very light.


Thanks.

Zenith CH-300 Driver.