Custom function quickstart

You can use Google Apps Script to write a custom function, then use it in Google Sheets just like a built-in function.

The following quickstart sample creates a custom function that calculates the sale price of discounted items. The sale price is formatted as US dollars.


  • Set up the script.
  • Run the script.


To use this sample, you need the following prerequisites:

  • A Google Account (Google Workspace accounts might require administrator approval).
  • A web browser with access to the internet.

Set up the script

  1. Create a new spreadsheet.
  2. From within your new spreadsheet, select the menu item Extensions > Apps Script.
  3. Delete any code in the script editor and paste in the code below. Then click Save Save icon.

     * Calculates the sale price of a value at a given discount.
     * The sale price is formatted as US dollars.
     * @param {number} input The value to discount.
     * @param {number} discount The discount to apply, such as .5 or 50%.
     * @return The sale price formatted as USD.
     * @customfunction
    function salePrice(input, discount) {
      let price = input - (input * discount);
      let dollarUS = Intl.NumberFormat("en-US", {
        style: "currency",
        currency: "USD",
      return dollarUS.format(price);

Run the script

  1. Switch back to your spreadsheet.
  2. In a cell, enter =salePrice(100,.2). The first parameter represents the original price and the second parameter represents the discount percentage. If you're in a location that uses decimal commas, you might need to enter =salePrice(100;0,2) instead.

The formula that you enter in the cell runs the function in the script you created in the previous section. The function results in a sale price of $80.00.

Next steps

To continue learning about how to extend Sheets with Apps Script, take a look at the following resources: