Which Aspect Ratio to Use for AI Images
Choose an image shape for its destination, set the ratio in LocalBanana, and calculate what a crop will remove. Includes geometric diagrams and the actual ratio menu.
On this page
Choose the shape of the image for the place it will be used. Set that shape in the aspect-ratio control, then use the prompt to describe where the subject and empty space should go.
This guide explains the geometry, shows the current LocalBanana setting, and gives you a way to check a crop before it cuts through something important.
Aspect ratio describes shape, not resolution
An aspect ratio is width : height. In 16:9, the image is wider than it is tall. In 9:16, it is taller than it is wide. In 1:1, the two sides are equal.
Pixel dimensions tell you how much image data you have. A 1000 × 1000 image and a 2000 × 2000 image are both 1:1. The larger file has more pixels, but the ratio alone says nothing about detail or image quality.
To simplify a ratio, divide width and height by their greatest common divisor. For example, dividing both 1920 and 1080 by 120 gives 16:9. If your destination specifies exact dimensions, use those to choose the shape and check the final pixel size separately.
Start with the destination
First inspect the actual frame: a website image slot, a slide, a printed area, or your device's display. Then decide what must fit inside it.
| If the layout needs… | Consider… | Check before you commit |
|---|---|---|
| A centered mark or an evenly divided grid | A square such as 1:1 | Will the final avatar or icon apply an additional circular crop? |
| A standing subject with space above and below | A portrait shape such as 3:4 or 4:5 | Do the head, hands, and important objects stay inside the frame? |
| A tall full-screen layout | A tall shape such as 9:16 | What is the actual screen ratio, and where do interface overlays sit? |
| A subject beside a headline or a wide scene | A landscape shape such as 16:9 | Is there enough room for both subject and text at the final display size? |
These are composition starting points, not platform specifications. A phone is not necessarily 9:16, and a social feed may have different rules for different placements. Check the destination's current requirements instead of assuming one ratio fits every use.
Set the ratio in LocalBanana
On the desktop interface, open Generate Image, choose a model, and open the ratio control beside the model selector. The control displays the current shape and ratio, such as Portrait 9:16.
- Open the ratio control.
- Expand the portrait, square, or landscape group to see its available ratios.
- Choose a ratio and check that the control now displays your selection.
- Write the prompt and review the other visible settings before generating. Sign in if the interface requires it.
View the complete interface screenshot.
Choose the model first, and recheck the ratio after changing models. Keep the prompt focused on composition. For example, after selecting a portrait ratio:
A full-length portrait with the entire head and shoes inside the frame.
Leave clear space above the head for a heading, and keep the hands away
from the left and right edges.
This is an example of describing placement, not a tested promise that the result will obey every boundary. Inspect the output before using it.
If you work on Midjourney's own interface, its official aspect-ratio documentation describes the --ar parameter. In LocalBanana, use the visible ratio control instead of assuming a parameter copied from another service configures the current model.
Changing the ratio can mean three different things
Generating again asks the model to create a new image on a different canvas. Subject placement and details can change, even if the text stays the same.
Cropping keeps existing pixels and removes the edges. It can improve composition when the important content already fits, but it cannot recover a hand or object that was outside the original image.
Adding space keeps the whole image within a larger canvas, or uses an editing process to create surrounding content. Plain margins are predictable; generated surroundings need checking because they are newly created. Do not stretch the image to make it fit: that changes the proportions of the subject.
Choose the method based on what must stay unchanged. If the exact existing image matters, inspect the crop or margin options first. If you need a substantially different composition, a new generation may be more appropriate.
Calculate the crop before cutting
Suppose your image is 1600 × 1600, and you want it to fill a 9:16 frame without stretching or margins.
Keeping the 1600-pixel height gives a target width of 1600 × 9 ÷ 16 = 900 pixels. A centered crop removes 350 pixels from each side. That is 43.75% of the original width in total, not 43.75% from each edge.
Now inspect those two strips. If either contains a hand, label, face, or other essential detail, move the crop where possible, leave margins, or choose another image. If the strips contain only expendable background, cropping may work well.
Check the finished image where it will be used
Before exporting or posting, check the actual destination preview:
- The downloaded image has the intended ratio and enough pixels for the placement.
- Faces, hands, logos, and text are clear of the final crop.
- Headings, controls, or interface overlays do not cover important content.
- The composition remains readable at its real display size, not just when enlarged.
For a phone background, continue with the wallpaper guide. For several panels in one image, the multi-panel guide explains how to plan the layout inside the canvas.
