How many bit strings are there of length 8 or less not count

How many bit strings are there of length 8 or less, not counting the empty string?

Solution

2^8 + 2^7 + 2^6 + 2^5 +2^4 + 2^3 + 2^2+2^1
= 256 + 128 + 64 + 32 + 16 + 8 + 4+2
= 510