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AI Image Size Calculator

Find the right resolution for SDXL, FLUX, DALL-E or Midjourney at any aspect ratio.

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Quick Tool Overview

The AI Image Size Calculator finds the best generation resolution for SDXL, SD 1.5, FLUX, DALL-E and Midjourney at any aspect ratio, then gives the crop to the exact ratio and the final size after upscaling.

What it does
Finds native generation sizes for AI image models
You give it
A model, an aspect ratio and an upscale factor
You get back
Generation size, crop size and final size
Best for
Stable Diffusion, ComfyUI, FLUX and Midjourney
AI Tools Free, unlimited use No sign-up Runs in your browser

About the AI Image Size Calculator

Image models are trained at particular sizes, and asking for anything else is how you get two heads, repeated subjects and stretched faces. SDXL was trained on a set of roughly one-megapixel buckets, SD 1.5 on 512 pixels, DALL-E accepts a short list of sizes, FLUX wants both sides divisible by 16, and Midjourney takes a ratio rather than pixels.

Choose the model and the aspect ratio the image is for — 16:9 for YouTube, 9:16 for stories, 4:5 for Instagram, 1.91:1 for link previews, or a custom ratio or final pixel size — and the calculator returns the best size to generate at, how far it is from your ratio, and every size the model is comfortable with, ranked by closeness.

Because the closest trained size is rarely exact, it also gives the crop that turns the generated frame into your precise ratio and the final dimensions after a 1.5, 2 or 4 times upscale — the full path from render to finished image. For Midjourney it writes the --ar value to add to your prompt.

Key features of the AI Image Size Calculator

Trained sizes per model

SDXL buckets, SD 1.5 sizes, FLUX multiples of 16, DALL-E fixed sizes and Midjourney ratios.

Ranked by closeness

Every supported size is listed with how far it is from your ratio.

Crop and upscale plan

The exact crop and final dimensions after a 1.5, 2 or 4 times upscale.

Platform presets

YouTube, stories, Instagram, link previews, headers and custom sizes.

Midjourney --ar output

The correct whole-number aspect ratio parameter for your prompt.

How to use the AI Image Size Calculator

  1. 1

    Choose the image model

    SDXL, SD 1.5, FLUX, DALL-E or Midjourney. Each has different native sizes.

  2. 2

    Choose the aspect ratio

    Pick where the image will be used, or type a custom ratio or final size.

  3. 3

    Set the upscale

    Choose the upscale you plan to apply with hires fix or an upscaler.

  4. 4

    Generate, crop and upscale

    Render at the suggested size, crop to the exact ratio, then upscale.

Frequently asked questions

SDXL was trained on buckets of about one megapixel, including 1024x1024, 1152x896, 1216x832, 1344x768 and 1536x640, plus their portrait versions. Sizes far from these produce more artefacts.

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