Just out of my own experience... we fly the Dash 8-300 to a 900 m-Runway (only in summer
) and depending on the wind, it can get a very tight calculation, where you start taking the QNH, every knot of wind, every ° Temperature in calculation.
As for 800 m, assumed no obstacle around:
No wind, no slope, flaps 15 and 800m would give you a take-off weight at sea-level of about 36000 lbs at 20° or just below 38000 ft at 0°.
Crew-version 2/2 and a light catering would give you a weight of about 27.000 pounds. Add about 2000 lbs of fuel (600 for half an hour reserve, about 700 for the half-hour flight, 200 taxi-fuel and 500 alternate about 15 mins away), and you look at a traffic-load of 7000 lbs at 20°C. That would mean: 37 pax, no luggage, or at 0°C: 9000 lbs: about 41 pax with 15 kg handluggage.
Hope that helps
Eli