In my usage, GNU units appears to be more featureful than qalc. For example I noticed that qalc lacks many definitions that I often use, such as energy density

In my usage, GNU units appears to be more featureful than qalc. For example I noticed that qalc lacks many definitions that I often use, such as energy density (eg. "gasoline"), mass density (eg. "golddensity"), energy units (eg. "therm"), astronomy (eg. "earthradius", "solarmass"), etc. And GNU units works just fine as a calculator. So, from my viewpoint, qalc is the "separate utility" that I don't need ;-)