Metric Units

What would the metric equations be please?

Eg. a 1.3 Litre 4 cylinder engine. I am confused when cubic inches are converted to cubic feet by dividing by 1728(VE calculation), and the 2.7 constant for Air Density. I'm worried that with one simple mistake I would get the whole thing wrong :/

I have prepared Excel page with all the conversion so I do not need to do it on paper every time. It saves time.