Assuming you are using the base of 10 in the log, I will refer to the log10 table.

`log 81 = log 3^4`

But according to logarithm laws, we know,

`log 3^4 = 4log3`

Therefore,

`log81 = 4log3`

We can refer to log10 table for log3.

`log 3 = 0.4771` (according to table)

Then,

`log81 = 4(0.4771)`

`log81 = 1.9084`

**The answer is 1.9084.**

**Further Reading**