Check the charts in the flight manual.
If you can't, then try the following:
- Note the power required to hover out of ground effect.
- Before you land, note the power to hover in ground effect.
- When you take off with 200# extra, note the increase. -
Apply the increase to the power required to hover out of ground effect (and a little bit extra).
Not scientific, but if for some reason you can't check the charts, then this could help. With a guess method like this, I would want to ensure a good power margin.