As long as all the units are in ml, you should also be able to use it for fl oz. Just pretend the ml actually say fl oz and the percentages should still all come out correct. I did not get a good look at the calculator but It looks like all the units are the same, correct? I did a similar calculator but mine is all in oz. and I have a few different calculators that will take an initial fuel and you can add components to it and see what you get in the end or actually tell it what you want in the end and get the correct ingredients to add to existing fuel to get the right ratios.

I eventually added ml unit conversion on to mine because when making small quantities of small percentages, an oz. is just a little too course to accurately measure.

Thanks for sharing.