How to get a percentage from a range [closed]

Question

I have a basic math question. I am trying to get a percentage from a range of numbers and the algorithm is troubling me.

Say I have a range of -5 to +5 and I want to know what percentage is in between given a value. I know that -5 would be equivalent to 0% and 5 would be 100%, with 0 being 50%.

I tried to add 5 to bring up the scale, but it just feels like a hack. I would like it to feel dynamic so that I can give it any range and successfully work.

Ex.

percent = (5 + value) * 100 / 10

How do I figure out what value should be the a general case?

Answer 1

range = top_value - bottom_value
percent = (value - bottom_value) / range