# Base Conversion Tool

## Bases Greater than 10

What happens when you need more than 10 digits?

## Undecimal (Base 11)

Undecimal (Base 11) needs one more digit than Decimal, so "A" is used, like this:

Decimal: | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | ... |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Undecimal: | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A |
10 | 11 | ... |

## Duodecimal (Base 12)

Duodecimal (Base 12) needs two more digits than Decimal, so "A" and "B" are used:

Decimal: | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | ... |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Duodecimal: | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A |
B |
10 | 11 | ... |

## Hexadecimal (Base 16)

Because there are more than 10 digits, hexadecimal is written using letters as well, like this:

Decimal: | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | ... |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Hexadecimal: | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A |
B |
C |
D |
E |
F |
10 | 11 | ... |

## Vigesimal (Base 20)

With vigesimal, the convention is that **I** is not used because it looks like **1**, so **J**=18 and **K**=19, as in this table:

Decimal: | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | ... |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Vigesimal: | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A |
B |
C |
D |
E |
F |
G |
H |
J |
K |
10 | ... |

## Letters (Base 26)

With "Base 26", you use the letters of the alphabet (not 0 to 9).

Some people start with A=0, B=1, etc. But it seems more natural to use A=1, B=2, etc, as everyone thinks that A is the first letter, B is the second, and so on.

So I use the A=1, B=2, convention, and I use "Z" for Zero! Like this:

Decimal: | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | ... |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Base 26: | Z |
A |
B |
C |
D |
E |
F |
G |
H |
I |
J |
K |
L |
M |
N |
O |
P |
Q |
R |
S |
T |
U |
V |
W |
X |
Y |
AZ |
AA |
... |

It is fun to use Base 26, type your name in, and see what number you are!

Also, try putting in decimal values after the ".", for example 0.1 produces "BOOO..."