Units is a wonderful program; don't be afraid to use their definitions (/usr/share/units/definitions.units): $ units -t '24816400 GWh / (1347000000 km^3) / w

Units is a wonderful program; don't be afraid to use their definitions (/usr/share/units/definitions.units): $ units -t '24816400 GWh / (1347000000 km^3) / waterdensity / water_specificheat' 1.5851925e-05 K There's even definitions like `oceanarea`, etc ;-)