1010 = 10₁₀

It is convenient to remember the above fact. If you know it, then it takes just a moment to recognize 1001 = 9₁₀, 1011 = 11₁₀, and others. To convert larger binary representations to decimal representation, use a table. You can create this table from scratch by muliplying the decimal values by two starting on the right.

Now think of the bits of the binary representation as turning on or off the numbers to include in the sum. For example, with 1010 1010 the various powers are turned on, as above.