Your reading is 24 or 25...

Try calculating 24/255*5v = 0.470v...

That's equivallent to ADCVoltage=ADCCount/ADCMaxScale*VRef

Close enough for you?

BTW... you can't use the above math in PBP as you have to scale it up a little to maintain INTEGER integrity, but I'm sure you can figure how to do that.

And in answer to a previous point you made right at the start, the reason 0-5v Sensors don't actually go 0-5v, is that by going say 0.5v-4.5v you can tell if they go open or short circuit or otherwise go defective as their output will be out of range by being too low or too high. If it actually started at 0v and somebody pulled the plug on the Sensor on your Hospitals Life Support machine, you'd never know - and just might wreck your day.