# Quick way to express percent from negative interval

I have some data which looks like this:

I get a number in the -6/+4 range and I need to express it with percent. If I get 4 of course the result is 100%, If I get -6 is 0%, etc.

Is there a quick formula I can use to obtain the percent value of, say, -3.25?

• I'm not sure if got the question, but your interval can be shifted in the interval $[0,10]$, now you multiply by $10$ and you get the percentage. Summarizing, take $x\in [-6,4]$ then your percentage is $((x+6)\cdot 10 )\%$. – Bman72 Jan 13 '15 at 12:18
• Say I have a -4.5/+4.5 range and I get a 0 value. Shouldn't that be equal to 50%? With you formula I get 45%. Am I doing something wrong? – JessyP Jan 13 '15 at 12:31

For $x \in [-6, 4]$ the function $$p(x) = \frac{x+6}{10}$$ is what you are looking for. You should note however that this gives numbers between $0$ and $1$. If you want the actual percentages, just use the function $$q(x) = p(x) * 100 = 10 (x + 6)$$ instead.
In general for an interval $[a, b]$ you can use the formulas $$p(x) = \frac {x-a} {b-a}$$ and $$q(x) = 100 * p (x) = 100 * \frac {x-a} {b-a}$$
• Please see my comment to the original question, how does this work in the case of a 0 value in a -4.5/+4.5 interval? – JessyP Jan 13 '15 at 12:35