Double Check Affix Math please

I wanted an easy way to check how good an affix rolled within a range.

The formula I came up with is

(Max)Roll - (Min)Roll + 1, gives (Range) of values.

(Actual) Roll - Min + 1= (Value) Within the Range.

(Value) / (Range) = (Percent) of possible max roll.

Sorry if this seems basic or obsessive. If another math geek wants to verify I would appreciate it. If there is another tool out there that already does this, I would love a link. Its easy enough to build it in sheets of course.