For those on a Mac the millilightseconds unit probably won't work, in which case you can try: 586 units, 56 prefixes You have: 3 lightyear / 365.25 / 24 /

For those on a Mac the millilightseconds unit probably won't work, in which case you can try: 586 units, 56 prefixes You have: 3 lightyear / 365.25 / 24 / 60 / 60 / 1000 You want: miles * 558.83525 / 0.0017894361