What is the best way to calculate log without a calculator? As the title states, I need to be able to calculate logs (base $10$) on paper without a calculator.
For example, how would I calculate $\log(25)$?

The algorithm is much older than Ezui: I have a booklet at home (written in dutch) from the 19th century, May 1st 1846, 2nd edition, Delft, NL, written by H. Strootman, lecturer at the Royal Academy in Delft, where the algorithm is explained in gory detail.
Entitled: "Iets over de LOGARITHMEN"  in english: "Some about LOGARITHMS"
It works for all bases g in e.g.  $\log g (X)$ in which case you  should not take the nearest power of 10 instead the nearest power of g:
so 10^n  becomes $g^n$ ....
It is from what I read in this pocketformat booklet the standard way how people computed logarithms those days ...
