An aspect ratio is the proportion of a picture's width to its height, written as two numbers such as 16:9. It describes the shape of the frame, not how many pixels it holds. 1:1 is a square, 16:9 is a wide screen and 9:16 is a phone held upright.
How to read a ratio
The first number is the width and the second is the height, in any unit. A 16:9 frame is sixteen parts wide for every nine parts tall, so 1920 by 1080 pixels and 1280 by 720 pixels are both 16:9. To compare shapes, divide width by height. 16:9 comes to about 1.78, 1:1 is exactly 1 and 4:5 is 0.8. Above 1 the frame is landscape, below 1 it is portrait, and 1 is a square.
The ratio is separate from resolution. Resolution counts pixels, while the ratio only fixes the shape those pixels sit in. A 4:5 image can be small or huge, and two images with the same pixel count can be square or wide.
The ratios AIGE offers for images
Choose the ratio before you generate, because the model composes the picture for the frame you give it. In the Canvas picture settings, Nano Banana 2 (labeled Nano 2.1 in the picker), Nano Banana Pro, Nano Banana Lite and GPT Image 2 offer nine ratios. Recraft 4.1 offers a shorter list of five.
Ratio | Shape | A shape you may know it from |
|---|---|---|
21:9 | Very wide | Banners, panoramas and a letterbox look |
16:9 | Wide | Widescreen TVs and monitors, and most video frames |
3:2 | Slightly wide | A classic 35 mm photo |
4:3 | Slightly wide | Older TV and monitor screens |
1:1 | Square | Profile pictures and grid tiles |
4:5 | Slightly tall | A portrait photo that fills more of a phone screen than a square does |
3:4 | Slightly tall | The upright twin of 4:3 |
2:3 | Tall | A 4 by 6 inch print held upright |
9:16 | Very tall | Full-screen vertical phone video |
On the Nano Banana models the credit price follows the size and never the ratio, so a 1:1 image and a 21:9 image at 1K both cost 8 credits on Nano Banana 2. GPT Image 2 is the exception. At 1K on Medium and High quality its price depends on the shape of the frame.
Video ratios depend on the model
Each video model accepts its own list, and the picker shows only the ratios the model you chose can take. Models also treat a start picture differently, so the table has two columns.
Model | Ratios when you write the shot | Ratios when you start from a picture |
|---|---|---|
Kling V3 | 16:9, 9:16, 1:1 | None to pick: the picture sets the shape |
Seedance 2.0 | 21:9, 16:9, 4:3, 1:1, 3:4, 9:16 | The same six |
Seedance 2.5 | 21:9, 16:9, 4:3, 1:1, 3:4, 9:16 | None to pick: the picture sets the shape |
Omni Flash | 16:9, 9:16 | The same two |
H3 Max | 21:9, 16:9, 4:3, 1:1, 3:4, 9:16 | None to pick: the picture sets the shape |
When a model reads the shape from the picture, give the picture the frame you want before you start the clip. With image-to-video on Kling V3, Seedance 2.5 or H3 Max, the first frame is the only say you get over the shape. Every model above offers 9:16 for vertical clips, and the AI video page lists the clip models side by side.
Picking a ratio before you generate
Start from where the picture will be seen. A square suits a profile picture or a grid tile, a tall frame fills a phone held upright and a wide frame fits a screen on its side. Then generate in that shape. Cropping a finished image to a narrower shape always works but throws pixels away. Extending an image to a wider shape means the new sides have to be invented.
If you are unsure, make one image in the shape you expect to use most and one in the next closest, then keep the better composition. At 1K on Nano Banana 2 each run costs 8 credits. The AI image generator page covers the models, and the Nano Banana page covers how that family handles sizes.
Honest note: These lists are what AIGE offers today. A model update can change one, and the picker always shows what the model you chose accepts.
Quick answers
Question | Answer |
|---|---|
What is an aspect ratio? | The proportion of width to height, written as two numbers like 16:9. It sets the shape of the frame, not its pixel count. |
What does 16:9 mean? | The frame is sixteen units wide for every nine units tall, about 1.78 times wider than it is tall. It is the usual widescreen shape. |
What aspect ratios can I use for AI images in AIGE? | Nine on the Nano Banana models and GPT Image 2: 21:9, 16:9, 3:2, 4:3, 1:1, 4:5, 3:4, 2:3 and 9:16. Recraft 4.1 offers five. |
Which aspect ratio makes a vertical video? | 9:16. Kling V3, Seedance 2.0 and 2.5, Omni Flash and H3 Max all offer it. |
What is the difference between aspect ratio and resolution? | The ratio is the shape of the frame, such as 4:5. Resolution is how many pixels fill it, such as 1K or 4K. |
Does the aspect ratio change what an AI image costs? | Not on the Nano Banana models, where the size sets the price. On GPT Image 2 at 1K the price varies with the shape of the frame on Medium and High quality. |
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