### How to convert column index into letters with Google Apps Script

Although Google Sheets does not provide a ready-to-use function that takes a column index as an input and returns corresponding letters as output, we can still do the task by leveraging other built-in functions ADDRESS, REGEXEXTRACT, INDEX, SPLIT as shown in the post. However, in form of a formula, that solution is not applicable for scripting with Google Apps Script. In this post, we look at how to write a utility function with Google Apps Script that converts column index into corresponding letters. ## Concept

With the solution in the form of a formula, we don't even need to understand how column index and letters map each other. With apps script, we need to understand the mapping to come up with an algorithm.

In a spreadsheet, columns are indexed alphabetically, starting from A.

• Obviously, the first 26 columns correspond to 26 alphabet characters, A to Z.
• The next 676 columns (26*26), from 27th to 702nd, are indexed with 2 letters. [AA, AB, ... AY, AZ], [BA, BB, ... BY, BZ], ... [MA, MB, ... MY, MZ], ... [ZA, ZB, ... ZY, ZZ]. Each alphabet character takes a turn (in order) to precede all 26 alphabet characters.
• The next 17576 columns (26*26*26), from 703rd to 18278th, are indexed with 3 letters. [AAA, AAB, ... AAY, AAZ], [ABA, ABB, ... ABY, ABZ], ... [ZZA, ZZB, ... ZZY, ZZZ]. Each letter AA to ZZ above takes a turn (in order) to precede all 26 alphabet characters.
• etc.

The above observation suggests a recursive pattern. Columns with 3 letters depend on columns with 2 letters, columns with 2 letters depend on columns with 1 letter. Moreover, the number of letters for a column depends on its index divided by 26. It suggests that we need to divide column index by 26 to apply the recursive pattern. So, here are the steps of the algorithm:

• let ALPHABETS=['A', 'B', 'C', 'D', ... 'X', 'Y', 'Z']
• if k <= 26, then return ALPHABETS[k - 1];
• else return getColumnLetters(k / 26) + ALPHABETS[(k % 26) - 1]
 Column Index Column Letters Divide by 26 12 L =12 13 M =13 26 Z =26 27 AA =1*26+1 37 AK =1*26+11 38 AL =1*26+12 53 BA =2*26+1 75 BW =2*26+23 988 AKZ =37*26+26 989 ALA =38*26+1 1390 BAL =53*26+12 1963 BWM =75*26+13

Let's take the column 1963rd as an example:

• As 1963=75*26+13, the 1963rd column letters are the concatenation of the 75th column letters and the 13th column letters.
• As 13 < 26, the 13rd column's letter is the 13rd alphabet character that is M.
• As 75 = 2 * 26 + 23, the 75th column letters are the concatenation of the 2nd column letters and the 23rd column letters.
• As 2 < 26, the 2nd column letter is the 2nd alphabet character that is B.
• As 23 < 26, the 23rd column letter is the 23rd alphabet character that is W.
• The 75th column letters are hence B + W = BW.
• The 1963rd column letters are hence BW + M = BWM.

Let's analyze the column 988th that is a little bit trickier because 988 is divisible by 26:

• As 988=38*26+0, the 988th column letters are the concatenation of the 38th column letters and the 0th column letters. But wait, column index starts from 1, doesn't it?.
• In fact, as 988 is divisible by 26, it can be expressed as 988=37*26+26. That means the 988th column letters are the concatenation of the 37th column letters and the 26th column letters.
• As 26 = 26, the 26th column letter is the 26th alphabet character that is Z.
• As 37 = 1 * 26 + 11, the 37th column letters are the concatenation of the 1st column's letter and the 11th column's letter.
• Because, 1 < 26, the 1st column letter is the 1st alphabet character that is A.
• As 11 < 26, the 11th column letter is the 11th alphabet character that is K.
• The 37th column letters are hence A + K = AK.
• The 988th column letters are hence AK + Z = AKZ.

To implement this algorithm in javascript, we need to pay attention to certain points:

• The column index, which is the input of the function, starts from 1, while the array in javascript starts from 0.
• When dividing the column index by 26, we need to round the result down.
• If the column index is divisible by 26, the residual is 0. To apply the next recursive call, we need to reduce the result by one while increasing the residual by 26.

## Demo

Finally, you can find below an example of code to convert column index into corresponding letters in Google Apps Script and a test function that prints out letters for all the first 1000 columns in 3 different ways that we have discovered in these 2 posts.

``````function getColumnLetters(columnIndexStartFromOne) {
const ALPHABETS = ['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', 'Z']

if (columnIndexStartFromOne < 27) {
return ALPHABETS[columnIndexStartFromOne - 1]
} else {
var res = columnIndexStartFromOne % 26
var div = Math.floor(columnIndexStartFromOne / 26)
if (res === 0) {
div = div - 1
res = 26
}
return getColumnLetters(div) + ALPHABETS[res - 1]
}
}
``````

``````function test() {
var rows = []
var row1 = []
var row2 = []
var row3 = []
var row4 = []
for(let i = 1; i < 1000; i++) {
row1.push(getColumnLetters(i))
row2.push(i)
row3.push('=REGEXEXTRACT(ADDRESS(1, ' + i + '),"\\\$([A-Za-z]+)\\\$")')
row4.push('=INDEX(SPLIT(ADDRESS(1, ' + i + '),"\$"),1,1)')
}
rows.push(row1, row2, row3, row4)

var sheetName = "test"
if (sheet) {
sheet.clear()
} else {
}
sheet.getRange(1, 1, rows.length, rows.length).setValues(rows)
}
``````

## Disclaimer

The post is only for informational purposes and not for trading purposes or financial advice.

## Feedback

If you have any feedback, question, or request please:

## Support this blog

If you value my work, please support me with as little as a cup of coffee! I appreciate it. Thank you!

If you read it this far, I hope you have enjoyed the content of this post. If you like it, share it with your friends!

1. Hello Friend, I found this and I think is better:

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;
}

1. Hi,

Nice way of using while loop instead of recursive programming.

### Use SPARKLINE to create 52-week range price indicator chart for stocks in Google Sheets

The 52-week range price indicator chart shows the relative position of the current price compared to the 52-week low and the 52-week high price. It visualizes whether the current price is closer to the 52-week low or the 52-week high price. In this post, I explain how to create a 52-week range price indicator chart for stocks by using the SPARKLINE function and the GOOGLEFINANCE function in Google Sheets.

### Compute cost basis of stocks with FIFO method in Google Sheets

After selling a portion of my holdings in a stock, the cost basis for the remain shares of that stock in my portfolio is not simply the sum of all transactions. When selling, I need to decide which shares I want to sell. One of the most common accounting methods is FIFO (first in, first out), meaning that the shares I bought earliest will be the shares I sell first. As you might already know, I use Google Sheets extensively to manage my stock portfolio investment, but, at the moment of writing this post, I find that Google Sheets does not provide a built-in formula for FIFO. Luckily, with lots of effort, I succeeded in building my own FIFO solution in Google Sheets, and I want to share it on this blog. In this post, I explain how to implement FIFO method in Google Sheets to compute cost basis in stocks investing.

### Use SPARKLINE column chart to create price chart with reference price

I own and follow several stocks in my investment portfolio. I pick a reference price for each stock. To effectively track the movement of a stock, I need to visualize its 52-week prices based on the reference price that I determined. In this post, I explain how to do so with the SPARKLINE column chart in Google Sheets.

### Slice array in Google Sheets

Many functions in Google Sheets return an array as the result. However, I find that there is a lack of built-in support functions in Google Sheets when working with an array. For example, the GOOGLEFINANCE function can return the historical prices of a stock as a table of two columns and the first-row being headers Date and Close. How can I ignore the headers or remove the headers from the results?

### Create a dividend income tracker with Google Sheets by simply using pivot tables

As my investment strategy is to buy stocks that pay regular and stable dividends during a long-term period, I need to monitor my dividends income by stocks, by months, and by years, so that I can answer quickly and exactly the following questions: How much dividend did I receive on a given month and a given year? How much dividend did I receive for a given stock in a given year? Have a given stock's annual dividend per share kept increasing gradually over years? Have a given stock's annual dividend yield been stable over years? In this post, I explain how to create a dividend tracker for a stock investment portfolio with Google Sheets by simply using pivot tables.

### How to copy data in Google Sheets as HTML table

I often need to extract some sample data in Google Sheets and present it in my blog as an HTML table. However, when copying a selected range in Google Sheets and paste it outside the Google Sheets, I only get plain text. In this post, I explain how to copy data in Google Sheets as an HTML table by writing a small Apps Script program.

### Compare stock investment portfolio to market indexes

As investors, we always want to see our portfolio grows over time. If a portfolio made a 1000\$ of gain in one year, is it good enough? Should we gauge the portfolio's performance against an alternative investment, for instance, a market index? Should we aim to beat that index? In this post, we will see how to compare a stock portfolio to market indexes by using Google Sheets, Apps Script, and Google Data Studio.