This number is equal to 158. How did I get that? Well, if you follow the table that I showed you in the beginning, the first digit is 1, followed by 2, and so on. Each place where there is a one, you add the number in that place to your total. So, since there's a 0 in the "1's" place, we don't add 1, but since there's a 1 in the "2's" place, we will add 2. There's a 1 in each of these places: 2, 4, 8, 16, and 128, so, 2+4+8+16+128=158. That's so easy isn't it? Here, try this one: 101010101. By the way, when doing this while at the computer, the scientific mode of Windows Calculator has a feature to convert between hexadecimal, decimal, octal, and binary. You should have gotten 341 if you did it right. That was easy wasn't it? To convert from decimal is much harder. You take the next lowest place value from your number (unless your number is the same as a place value, such as 32), and you divide your number by that place, take the remainder, rinse and repeat until you get to 1. So, if our number was 100, we would divide it by 64, and get 36. We would then divide that by 32, and get 4. We divide 4 by 4, and get 1. Then we make our number and put a 1 in every place that we divided by. So, 100 in binary is 1100100.