Calculate algorithm's MIPS from cycles?
The CPU's datasheet will provide information about how many cycles each command requires (e.g. in here look for "cycles", and with something like this you can also work out what else might a command require to determine if additional cycles will be required). Sometimes they might differ (for the same command), depending on the operands. 

What you can do is disassemble the processing part, look at the set (i.e. unique) of commands that are used, look up how many cycles they take on average and from that, work-out a best-case / worst-case scenario for your algorithm (taking also into account how many times each command is used, potentially even, in a loop).

If you are already at a low-enough level, so that you are sure about what commands have been used, then your estimate will be closer to the real value.

Hope this helps.