Calculating bits required to store decimal number

Question

This is a homework question that I am stuck with.

Consider unsigned integer representation. How many bits will be required to store a decimal number

Answer 1

This one works!

floor(loge(n) / loge(2)) + 1

To include negative numbers, you can add an extra bit to specify the sign.

floor(loge(abs(n)) / loge(2)) + 2