1020 g shown as pounds and ounces
Our converter works its sums out.
We give the results in stones, pounds (lb) and ounces (oz), not as decimal fractions of a pound (2.nn lb).
If you need the actual formulas so you can make your own calculations to scientific accuracy, Wikipedia has a brilliant article covering Conversion of Units that covers a huge number of formulas for every conceivable unit of measurement
I only shown the units with more than 10 formulas, showing: (unit of measurement: number of formulas) in the Wiki article
length:69, area:36, volume:98, density:13, time:38, speed:17, acceleration:12, force:1a, pressure:22, energy:42, power:27
Just reading it should keep you busy for a while!