Bases - What are They? (Part 3) How to change base 2 numbers into base 10

Filed under: how numbers work; Author: Brian; Posted: August 10, 2008 at 6:45 pm;

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This short lesson is a continuation of the posts at:

In those lessons, we talked about what bases are, what they’re used for, and how to change numbers from base 10 to base 2 (easy!)

It’s even easier to change numbers from base 2 into base 10.

When you read a number in base 2,  you simply have to add the columns together that have a 1 in them, and ignore the columns with a 0 in them. 

In the number 111(base 2) there is a 1 in the fours, twos, and ones columns. Simply add 4, 2, and 1 to get the base 10 value, which is 7

The number 10110 has a 1 in the sixteens column, another in the fours column, and another in the twos column. So add 16 + 4 + 2, to give you 22, base 10.

You have to admit that’s pretty easy. 

What would the number 110101 (base 2) be, in base 10?

Answer it in a comment, if you like.



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1 Comment »

  1. Comment by Steph

    Let’s see … 110101 in base 2 — converted to base 10 — is 32+16+4+1=53??

    I remember being briefly exposed to bases in school … but no one really explained them or thought to mention why they were important. of course this was back in the day when computers weren’t a part of most people’s everyday experiences.

    Thanks for posting the clear, informative articles.

    Professor Homunculus sez:

    Yup, you nailed it right on the bean. And thanks for your nice comment.

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