AI Image Generation: Width and Height Guide

When generating images with AI models like Stable Diffusion, Flux, and other image generation models, the width and height parameters are crucial settings that significantly affect your final result.

Width and height determine both the size and aspect ratio of your generated image. Each AI model has an optimal range of dimensions where it performs best, based on the resolution it was trained on.

Quick Reference Tool

For pixel-perfect dimensions optimized for any AI model, use our AI Image Aspect Ratio Calculator. It provides one-click copying of dimensions in multiple formats with real-time megapixel calculation and constraint validation.

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Optimal Dimensions by Model

Stable Diffusion Models

Model	Resolution	Notes
Stable Diffusion 1.5	512×512 pixels (1:1)	Trained on 512px resolution
Stable Diffusion 2.1	768×768 pixels (1:1)	Trained on 768px resolution
Stable Diffusion XL (SDXL)	1024×1024 pixels (1:1)	Trained on 1024px with 15+ supported aspect ratios
SDXL Turbo	512×512 pixels	Optimized for speed at lower resolution
SDXL Lightning	1024×1024 pixels	Same as SDXL base
Pony Diffusion	1024×1024 pixels	SDXL-based

Modern AI Image Models

Model	Resolution	Notes
Flux Dev	1024×1024 or 1MP equivalents	Flexible megapixel targeting with 32px increment constraints
Flux Schnell	Same as Flux Dev	Optimized for speed
Hunyuan DiT	1024×1024 pixels	Recommended
Qwen VL (Image)	1024×1024 or higher	Flexible dimensions
Kolors	1024×1024 pixels	Similar to SDXL

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SDXL Supported Aspect Ratios

SDXL natively supports these resolutions for optimal quality:

Width × Height	Aspect Ratio	Use Case
1024 × 1024	1:1 (square)	Social media, icons
1152 × 896	9:7	Portrait orientation
896 × 1152	7:9	Portrait orientation
1216 × 832	19:13	Landscape photos
832 × 1216	13:19	Portrait photos
1344 × 768	7:4	Wide landscape
768 × 1344	4:7	Tall portrait
1536 × 640	12:5	Ultra-wide
640 × 1536	5:12	Ultra-tall

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Flux Dev Recommended Dimensions

Flux Dev works with dynamic megapixel targeting and requires dimensions in 32px increments:

Width × Height	Aspect Ratio	Megapixels
1024 × 1024	1:1	~1.0 MP
1344 × 768	16:9	~1.0 MP
768 × 1344	9:16	~1.0 MP
1216 × 832	3:2	~1.0 MP
832 × 1216	2:3	~1.0 MP
1536 × 1024	3:2	~1.6 MP
1024 × 1536	2:3	~1.6 MP

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Legacy Models

For older Stable Diffusion models, here are the recommended dimensions:

Width × Height	Aspect Ratio	SD 1.5	SD 2.1
512 × 512	1:1 (square)	✓	–
768 × 512	3:2	✓	–
512 × 768	2:3	✓	–
768 × 576	4:3	✓	–
896 × 512	16:9	✓	–
768 × 768	1:1 (square)	–	✓
1152 × 768	3:2	–	✓
768 × 1152	2:3	–	✓
1024 × 768	4:3	–	✓
1152 × 648	16:9	–	✓

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Best Practices

• Stay close to training resolution: Each model performs best at or near its native training resolution
• Respect minimum dimensions: Never go below the minimum edge length the model was trained on (512px for SD 1.5, 768px for SD 2.1, 1024px for SDXL/Flux)
• Use proper constraints: Many models require dimensions divisible by 8, 32, or 64 pixels
• Consider megapixels: Higher megapixel values mean slower inference. Lower resolutions generate faster
• Match aspect ratio to content: Use portrait ratios for people, landscape for scenery, square for social media
• Use the calculator: Visit aspect.promptingpixels.com for pixel-perfect dimensions that avoid generation errors

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Impact on Quality

Different aspect ratios and dimensions can significantly influence the final output quality:

• Images generated at non-native resolutions may show artifacts or reduced quality
• Extreme aspect ratios (like 16:9) work better with SDXL and Flux than older models
• Upscaling from native resolution often produces better results than generating at high resolution directly
• Composition and framing can be affected by aspect ratio choice

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Video Generation Models

Note: Some AI models like Wan 2.2 are designed for video generation (text-to-video and image-to-video) rather than static image generation. These models have different resolution requirements.

Model	Supported Resolutions	Details
Wan 2.2 T2V	480P, 720P	Generates 5-second videos at 24fps using 1280×720 (720P) or 854×480 (480P)