We just found UnitConversion.org, an online unit converter with auto-complete and a pretty large database of odd units. It looks like a a great tool, although it is inexplicably lacking the Debye (which we were trying to convert to electron Angstroms).

My favorite scientific unit has always been the **barn** (1 barn = 10^{-24} cm^{2}), which is a unit of cross-sectional area. I.e. hitting this nucleus should be as easy as hitting the side of a barn… Quadrupole moments can be expressed as electron-barns, and our group code uses this unit internally just because it amuses us.

It is interesting to note the following conversions:

- 1 barn = 1.072505996 x 10
^{-36}township - 1 barn = 1.544408634 x 10
^{-34}homestead - 1 barn = 2.471053815 x 10
^{-32}acre

Apparently, physicists have very small farms.

[tags]units[/tags]

Are you also aware of http://www.onlineconversion.com?

Check out Frink

It seems to cover most unit conversions and a lot of useful math, physics, etc. Even better, you can download the Java for desktop use (alas, it’s not currently open source).

I’m the developer of Frink, and I just found this in my referrer logs. I noticed, ironically, that the conversions you cite are all three slightly wrong.

They apparently make the common but very wrong error of not using *survey* feet or statute miles in defining the acre, township, or homestead. The survey foot is larger than the “international” foot by a factor of exactly 500000/499999, (same factor is true for statute mile/”international” mile.) The exact conversion for barn->acre is exactly:

15499969/627264000000000000000000000000000000000 (approx. 2.4710439304662786e-32)

You’ll find Frink to be better-researched and more authoritative, I hope.

Checkout this auto complete unit converter that understand the units as mathematical expressions