Resize Images for Google PMax Ads Using ChatGPT

◆ Google PMax Required Image Sizes

Performance Max campaigns need these three image sizes for full ad coverage:

Size	Dimensions	Aspect Ratio	Used For
Landscape	1200 × 628	~1.91:1	Display, Discover, Gmail ads
Square	1200 × 1200	1:1	Display, Discover, social placements
Portrait	960 × 1200	4:5	Mobile Display, Discover feed

◆ What You Need

ChatGPT with GPT-4o can resize images directly inside the chat — no Photoshop or extra tools needed.

A ChatGPT Plus, Pro, or Team account (image generation included)
The client image you want to resize (PNG, JPG, or WebP)

Open ChatGPT

Go to chatgpt.com or open the ChatGPT desktop/mobile app. Start a new chat and make sure the model selector shows GPT-4o — this is the model with built-in image generation and editing.

ChatGPT new chat screen with GPT-4o selected

Upload Your Image

Click the paperclip icon (attachment button) in the message bar, then select your image file. You can also drag and drop the image directly into the chat.

Tip: You can upload multiple images at once if you need to resize a batch. ChatGPT will process them together.

Write Your Resize Prompt

With the image attached, type a prompt telling ChatGPT the exact PMax sizes you need. Here are prompts you can copy and paste:

All 3 PMax Sizes at Once (Recommended) I need this image resized for Google Performance Max ads. Please give me three versions: 1. 1200 x 628 pixels (landscape) 2. 1200 x 1200 pixels (square) 3. 960 x 1200 pixels (portrait) Keep the subject centered and maintain high quality. Don't stretch or distort the image — if you need to fill extra space, extend the background naturally.

Landscape Only (1200x628) Resize this image to exactly 1200 x 628 pixels for a Google PMax landscape ad. Keep the main subject centered and the quality high. Don't crop out important elements.

Square Only (1200x1200) Resize this image to exactly 1200 x 1200 pixels (square) for a Google PMax ad. Keep the subject centered. If the original isn't square, extend the background naturally instead of stretching.

Portrait Only (960x1200) Resize this image to exactly 960 x 1200 pixels (portrait) for a Google PMax ad. Keep the subject centered and maintain high quality.

Send and Wait for the Result

Press Enter (or click the send arrow). ChatGPT will process your image and generate a resized version. This usually takes 10–30 seconds.

The resized image will appear directly in the chat as an inline image.

Note: ChatGPT regenerates the image using AI, so minor visual differences from the original are possible. For pixel-perfect resizing with zero changes, a traditional image editor is more reliable.

Download the Resized Image

Hover over the generated image and click the download button (down arrow icon) in the top-right corner. The image saves as a PNG file to your Downloads folder.

Tip: Need a different format? Ask ChatGPT: "Can you give me this as a JPG instead?"

Verify & Adjust if Needed

Check the output dimensions by right-clicking the downloaded file and viewing its properties. If the size isn't right, reply in the same chat:

Correction Prompt That's close, but the landscape version needs to be exactly 1200 x 628 pixels (not 1200 x 630). Please regenerate at the exact size.

ChatGPT keeps context from the conversation, so it will refine without needing to re-upload.

◆ Google PMax Image Specs — Quick Reference

All three sizes are required for full PMax ad coverage. Google recommends uploading at least one of each.

Format	Dimensions	Ratio	Min Required	Max Upload
Landscape	1200 × 628	1.91:1	1 image	20 images
Square	1200 × 1200	1:1	1 image	20 images
Portrait	960 × 1200	4:5	1 image	20 images

Google requirements: Max file size 5 MB. Accepted formats: JPG and PNG. Avoid excessive text on images — Google may reject ads with too much text overlay.

◆ Pro Tips for PMax Images

Request all 3 sizes in one prompt — saves time and keeps the look consistent across formats.
Say "extend the background" — when going from landscape to portrait (or vice versa), ChatGPT will fill in the edges naturally instead of stretching.
Keep the subject centered — Google crops images differently on different placements, so center-weighted compositions work best.
Avoid text on images — Google may reject PMax ads with too much text overlay. If the client image has text, ask ChatGPT to keep it minimal.
Verify exact dimensions — right-click the downloaded file → Properties to confirm. Google is strict about 1200×628 (not 1200×630).
Save as JPG under 5 MB — if the PNG is too large, ask ChatGPT: "Give me this as a JPG".
Follow up in the same chat — ChatGPT remembers your image, so you can request additional sizes without re-uploading.