# column number to letter apps script

## Column Number to Letter Apps Script

Have you ever needed to convert a column number to its corresponding letter in Google Sheets? It's a common problem that can be easily solved with an Apps Script function. In this blog post, we'll show you how to do just that!

### The Problem

Let's say you have a Google Sheet with a bunch of columns labeled A, B, C, etc. But instead of referring to columns by their letters, you want to refer to them by their numbers. For example, instead of writing "=A1+B1", you want to write "=1+2". How do you convert the column numbers to letters?

### The Solution

Luckily, Apps Script has a built-in function called "String.fromCharCode()" that can convert ASCII codes to their corresponding letters. We can use this function to convert column numbers to letters. Here's the code:

```
function columnToLetter(column) {
var temp, letter = '';
while (column > 0) {
temp = (column - 1) % 26;
letter = String.fromCharCode(temp + 65) + letter;
column = (column - temp - 1) / 26;
}
return letter;
}
```

Let's break down how this code works:

- We start by declaring two variables: "temp" and "letter".
- We enter a while loop that runs as long as the variable "column" is greater than zero.
- Inside the while loop, we calculate the remainder of "column - 1" divided by 26. This gives us the index of the letter we need to add to our "letter" variable.
- We use the "String.fromCharCode()" function to convert the index to its corresponding letter.
- We add the letter to the beginning of our "letter" variable.
- We calculate the new value of "column" by subtracting "temp" and 1 from it, and then dividing the result by 26.
- We return the final value of "letter".

### Using the Function

Now that we have our function, we can use it to convert column numbers to letters in our Google Sheets formulas. Here's an example:

```
function myFunction() {
var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
var columnNumber = 1;
var columnLetter = columnToLetter(columnNumber);
var cell = sheet.getRange(columnLetter + '1');
cell.setValue('Hello, World!');
}
```

In this example, we're setting the value of cell A1 to "Hello, World!" using the "columnToLetter()" function to convert the column number to its corresponding letter.

### Alternative Solution

Another way to convert column numbers to letters is to use the "num2col()" function from the "tabletop.js" library. Here's an example:

```
function myFunction() {
var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
var columnNumber = 1;
var columnLetter = Tabletop.num2col(columnNumber);
var cell = sheet.getRange(columnLetter + '1');
cell.setValue('Hello, World!');
}
```

This solution is shorter and simpler, but it requires you to load the "tabletop.js" library into your project.

### Conclusion

Converting column numbers to letters in Google Sheets can be a tricky problem, but with the help of Apps Script, it's easy to solve. Whether you choose to use the built-in "String.fromCharCode()" function or the "num2col()" function from the "tabletop.js" library, you'll be able to convert column numbers to letters in no time!