Can the RTX 4090 Laptop 16 GB run Z-Image (base)?
Yes, but only just: 16-bit leaves 1.7 GB free on the RTX 4090 Laptop 16 GB.
16-bit (12.3 GB) fits with only 1.7 GB to spare (about 14.3 GB of 16 GB).
01What to download
| Part | File | Folder | Size | |
|---|---|---|---|---|
| Model | z_image_bf16.safetensors 16-bit · Comfy-Org/z_image | models/diffusion_models | 12.3 GB | Download → |
| Text encoder | qwen_3_4b_fp8_mixed.safetensors Qwen3 4B FP8 · Comfy-Org/z_image | models/text_encoders | 5.6 GB | Download → |
| VAE | ae.safetensors FLUX.1 VAE (ae) · Comfy-Org/z_image | models/vae | 0.3 GB | Download → |
| Total download · keep about the same free on disk | 18.3 GB | |||
Alternatives: Qwen3 4B BF16 (8.0 GB). Sizes from Hugging Face, 2026-10-01.
Free ComfyUI workflow, tested on my RTX 5060 Ti: 16-bit workflow (.json). Drag the file into ComfyUI. All workflows →
02Every Z-Image file on 16 GB
| File | Size | Needed | On this card | Quality | Download |
|---|---|---|---|---|---|
| 16-bit ← SAFETENSORS · Comfy-Org | 12.3 GB | 14.3 GB | fits · 1.7 GB spare | the original weights | Hugging Face → |
| INT8 SAFETENSORS · Comfy-Org | 6.2 GB | 8.2 GB | fits · 7.8 GB spare | practically identical to the original | Hugging Face → |
| Q8_0 GGUF · unsloth | 7.2 GB | 9.2 GB | fits · 6.8 GB spare | practically identical to the original | Hugging Face → |
| Q6_K GGUF · unsloth | 6.1 GB | 8.1 GB | fits · 7.9 GB spare | very close to the original | Hugging Face → |
| Q5_K_M GGUF · unsloth | 5.6 GB | 7.6 GB | fits · 8.4 GB spare | close; small differences in fine detail | Hugging Face → |
| Q4_K_M GGUF · unsloth | 5.1 GB | 7.1 GB | fits · 8.9 GB spare | good; some loss in fine detail and text | Hugging Face → |
| Q3_K_M GGUF · unsloth | 4.6 GB | 6.6 GB | fits · 9.4 GB spare | noticeable loss of detail | Hugging Face → |
| Q2_K GGUF · unsloth | 4.0 GB | 6.0 GB | fits · 10.0 GB spare | heavy loss; a last resort | Hugging Face → |
“Needed” adds 1.2 GB of working memory for Z-Image and a 0.8 GB reserve. Sizes 2026-10-01.
03Measured and reported results
Nobody has sent measured numbers for this pair yet. If you run Z-Image on a RTX 4090 Laptop 16 GB, send your time per image and peak VRAM and it will appear here, credited.
04About the RTX 4090 Laptop 16 GB
The RTX 4090 Laptop 16 GB is an Ada Lovelace GPU with hardware FP8, so ComfyUI can compute Comfy-Org's FP8 files natively: small and fast. (Plain FP8 files use FP8 maths with the --fast fp8_matrix_mult option.) As a laptop GPU it runs at a lower power limit than desktop cards (80–150 W depending on the laptop). The memory verdicts are the same; speed depends heavily on how much power the laptop maker allows.
16 GB GDDR6 · 256-bit · Ada Lovelace · 80–150 W. Everything that runs on it →
05Questions
How much VRAM does Z-Image need?
Around 6.0 GB with the smallest file (Q2_K) and 8.2 GB with an 8-bit file (INT8). The full 16-bit file needs about 14.3 GB.
Which Z-Image file should I download for the RTX 4090 Laptop 16 GB?
16-bit (12.3 GB) from Comfy-Org/z_image.
How much do I need to download for Z-Image on the RTX 4090 Laptop 16 GB?
18.3 GB: z_image_bf16.safetensors, qwen_3_4b_fp8_mixed.safetensors, ae.safetensors.