## Example PHP code to convert a number to an Excel column letter

I was looking for a good way to convert a number to the Excel column letter, for example:

1 -> A
26 -> Z
27 -> AA
28 -> AB
800 -> ADT

etc.

After searching on Google, I could not find any algorithm I want. (The closest one can handle up to two letters, i.e., ZZ. It will crash if the number is too large.). So I ended up creating my own.

Basically, you can think of this problem as a 26 based number conversion. Here is the php version. It should be pretty simple to convert it to a different language. Let me know if you have any problem.

```function columnLetter(\$c){

\$c = intval(\$c);
if (\$c < = 0) return '';

\$letter = '';

while(\$c != 0){
\$p = (\$c - 1) % 26;
\$c = intval((\$c - \$p) / 26);
\$letter = chr(65 + \$p) . \$letter;
}

return \$letter;

}

```
```Usage:
columnLetter(1303618093);    //DERRICK
```

Note that if you prefer lower cases rather than upper cases, you can simply replace 65 by 96 in the code.

Enjoy~!

–Derrick

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## 8 Replies to “Example PHP code to convert a number to an Excel column letter”

1. Anonymous

Thank you so much !! At least THE real algo than can handle more than 2 letters ๐
I’ve tried to find it by my own, but i failed. Not a real 26 based number in fact, as the “0” digit is skeeped.

2. Brent Kelly

Here goes an inverse function of this to convert back from a column letter to a number.
Supports up to 3 letters to col ‘ZZZ’.

function column_number(\$col){
\$col = str_pad(\$col,3,’0′,STR_PAD_LEFT);
\$i = 0;
if (\$col{0} != ‘0’) {
\$i = ((ord(\$col{0}) – 64) * 676)+26;
\$i += (\$col{1} == ‘0’) ? 0 : (ord(\$col{1}) – 65) * 26;
} else {
\$i += (\$col{1} == ‘0’) ? 0 : (ord(\$col{1}) – 64) * 26;
}
\$i += ord(\$col{2}) – 64;
return \$i;
}

3. Carlos Diaz

Undefined variable: letter

Last line of “while” loop… \$letter = chr(65 + \$p) . \$letter;
Last \$letter is not defined.