The length of runway required for take-off; for landing; in an emergency is determined by the weight of the aircraft [on the day]; the take-off distance available [TODA] AND the prevailing weather conditions.....particularly surface wind and temperature. Whether the runway is wet or dry or otherwise contaminated also affects the calculation.
So a whole range of variables which vary from flight to flight, from day to day and airfield to airfield.
Just my two penneth which may help some of the less well informed.
H49