Calibrating sensors - should be easy?

Hi,
Whats the equation for constraining a variable to a specific scale i.e. I have a light sensor that outputs an analog read value between 200 - 800 which I want to convert to a scale of 0-255
Ta for any help:)
Tom

OK found this:
http://www.arduino.cc/playground/Main/Fscale

which will convert one scale to another, but this seems like overkill as im only using integers - I do wish I was better at maths;)

Tom

Here is the integer-version of the scale function you where looking for...
http://www.arduino.cc/playground/Main/Autoscale

Never used it myself, I simply knew by accident it was somewhere on the playground...

Eberhard

Great,
Thanks for that Eberhard.
Tom