How to Make OpenAI API calls from Google Sheets?

I often have a need of making OpenAI API calls directly from Google Sheets to prepare some data.

Earlier, I used to use Add-Ons like GPT for Sheets, but slowly they all became paid.

So I figured a free alternative for my needs. I’m sharing it here so you all can use it as well.

Step 1: Generate OpenAI API Key

Go to this link : https://platform.openai.com/api-keys

Click on “Create new secret key”

Give it a name so you can identify where the key was used.

Copy the key as you will need it later.

Step 2: Create an App Script

This will bring you to a view like this.

Remove everything from the code section, and Paste this code into the App Script

Apps Script Code

function GPT(prompt, systemMessage, temperature, model) {
  const apiKey = 'YOUR_OPENAI_API_KEY'; // Replace this securely
  const url = 'https://api.openai.com/v1/chat/completions';

  // Set defaults if values are not provided
  systemMessage = systemMessage || "You are a helpful assistant.";
  temperature = typeof temperature === 'number' ? temperature : 0.7;
  model = model || "gpt-4o";

  if (!prompt || prompt.trim() === "") {
    return "❌ Please provide a prompt.";
  }

  const payload = {
    model: model,
    messages: [
      { role: "system", content: systemMessage },
      { role: "user", content: prompt }
    ],
    temperature: temperature
  };

  const options = {
    method: 'post',
    contentType: 'application/json',
    headers: {
      Authorization: 'Bearer ' + apiKey
    },
    payload: JSON.stringify(payload),
    muteHttpExceptions: true
  };

  try {
    const response = UrlFetchApp.fetch(url, options);
    const json = JSON.parse(response.getContentText());

    if (!json.choices || !json.choices[0]) {
      return "⚠️ No response from OpenAI.";
    }

    return json.choices[0].message.content.trim();
  } catch (e) {
    return "❌ Error: " + e.message;
  }
}

Replace YOUR_OPENAI_API_KEY with your own API Key that you generated.

Click on Save Button.

Step 3: Make an OpenAI call from Google Sheet.

Now go to your Google Sheet, and you can make an API call.

It should return a response like this.

To make the experience a little bit better, I’ve baked in some customization like model selection, system prompt, temperature and error handling. Here are some examples of how you can use them all.

🚀 You’re All Set!

With just a few lines of code, you’ve unlocked the power of GPT right inside Google Sheets — totally free.