> One can convert between decimal and other bases (radices) using bc, by
> setting the input or output base:
[...]
> For more general radix conversion, I use db:

to add my own 2 cents, i tend to use a little command-line
calculator i wrote ages ago to do this sort of thing.

i still prefer it to the above tools because it's not interactive
(= less stuff to type to get the results).

it's a reverse polish calculator, which works quite well
on the command line, as there's almost no punctuation
to get in the way of the shell's syntax (no brackets, and the
stuff to be executed is just a list of operands/operators, which
maps well to rc's lists). it's also handy for building up an expression
incrementally.

it's very similar to the inferno version, documented at
http://www.vitanuova.com/inferno/man/1/fc.html

all calculations are done in floating point, and it's a convenient
command-line way of getting access to the floating point
library, not to mention converting between bases.

e.g.
% fc 0x400
1024
% fc -x 1024
0x400
% fc 0400
256
% fc -x 0400
0x100
% fc 22 7 /
3.142857143
% x=(1 2 3 4 5 6)
% fc $x sum
21
% fc -B 96451234
0b00000101101111111011101010100010
  10987654321098765432109876543210
   3         2         1
% fc 0b00000101101111111011101010100010 sqrt
9820.958914
% fc -help
Usage: fc -[dcxotbB] <postfix expression>
Option specifies output format:
		-d decimal
		-c rune
		-x hex
		-o octal
		-t time
		-b binary
		-B annotated binary
Operands are decimal(default), hex(0x), octal(0), binary(0b),
             rune(@), time(hh:mm.ss)
Operators are: (number of arguments in brackets)
swap[2] dup[1] rep[n] ![1] %[2] p[1] *,×,x[2] **,xx,^,pow[2] 
+[2] -[2] /[2] _[1] <<,«,shl[2] >>,»,shr[2] and,⋀[2] ⋁,or[2] 
xor[2] not[1] sum[n] acos[1] asin[1] atan[1] atan2[2] ceil[1] 
cos[1] cosh[1] deg[1] exp[1] fabs[1] floor[1] fmod[2] ldexp[2] 
log,ln[1] log10[1] log2[1] rad[1] sin[1] sinh[1] √,sqrt[1] 
tan[1] tanh[1] trunc[2] 
Constants are:
	π=3.14159
	pi=3.14159
	e=2.71828
% 

i've attached it. someone might find it useful.