Can the RTX 4090 24 GB run FLUX.2 [dev]?
Not at full quality. The 16-bit and 8-bit files are too big for the RTX 4090 24 GB; the largest that fits is Q4_K_M (20.1 GB).
Q4_K_M (20.1 GB) fits with only 0.6 GB to spare (about 23.4 GB of 24 GB). Quality: good; some loss in fine detail and text.
Also try the FP8 file (35.5 GB) on this GPU. It does not fit entirely, but a current ComfyUI streams the overflow from RAM and native 8-bit files often beat a small GGUF that does fit. Dynamic VRAM →
01What to download
| Part | File | Folder | Size | |
|---|---|---|---|---|
| Model | flux2-dev-Q4_K_M.gguf Q4_K_M · city96/FLUX.2-dev-gguf | models/unet | 20.1 GB | Download → |
| Text encoder | mistral_3_small_flux2_fp8.safetensors Mistral 3 Small FP8 · Comfy-Org/flux2-dev | models/text_encoders | 18.0 GB | Download → |
| VAE | flux2-vae.safetensors FLUX.2 VAE · Comfy-Org/flux2-dev | models/vae | 0.3 GB | Download → |
| Total download · keep about the same free on disk | 38.5 GB | |||
Alternatives: Mistral 3 Small BF16 (35.6 GB). Sizes from Hugging Face, 2026-10-01.
System RAM: 48 GB or more. These files take about 38.5 GB of RAM while loaded, 44.5 GB with Windows and ComfyUI. What happens with less. calculated
02Every FLUX.2 dev file on 24 GB
| File | Size | Needed | On this card | Quality | Download |
|---|---|---|---|---|---|
| 16-bit SAFETENSORS · black-forest-labs | 64.4 GB | 67.7 GB | 43.7 GB too big | the original weights | Hugging Face → |
| FP8 SAFETENSORS · Comfy-Org | 35.5 GB | 38.8 GB | 14.8 GB too big | practically identical to the original | Hugging Face → |
| Q8_0 GGUF · city96 | 35.0 GB | 38.3 GB | 14.3 GB too big | practically identical to the original | Hugging Face → |
| Q6_K GGUF · city96 | 27.4 GB | 30.7 GB | 6.7 GB too big | very close to the original | Hugging Face → |
| Q5_K_M GGUF · city96 | 24.1 GB | 27.4 GB | 3.4 GB too big | close; small differences in fine detail | Hugging Face → |
| Q4_K_M ← GGUF · city96 | 20.1 GB | 23.4 GB | fits · 0.6 GB spare | good; some loss in fine detail and text | Hugging Face → |
| Q3_K_M GGUF · city96 | 16.0 GB | 19.3 GB | fits · 4.7 GB spare | noticeable loss of detail | Hugging Face → |
| Q2_K GGUF · city96 | 12.9 GB | 16.2 GB | fits · 7.8 GB spare | heavy loss; a last resort | Hugging Face → |
“Needed” adds 2.5 GB of working memory for FLUX.2 dev 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 FLUX.2 dev on a RTX 4090 24 GB, send your time per image and peak VRAM and it will appear here, credited.
04With more VRAM
With 48 GB you could run FLUX.2 dev at 8-bit or better (FP8, 35.5 GB) with no offloading.
What changes from the RTX 4090 24 GB to the RTX 5090 32 GB →
05About the RTX 4090 24 GB
The RTX 4090 24 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.)
24 GB GDDR6X · 384-bit · 1008 GB/s · Ada Lovelace. Everything that runs on it →
06Questions
How much VRAM does FLUX.2 dev need?
Around 16.2 GB with the smallest file (Q2_K) and 38.8 GB with an 8-bit file (FP8). The full 16-bit file needs about 67.7 GB.
Which FLUX.2 dev file should I download for the RTX 4090 24 GB?
Q4_K_M (20.1 GB) from city96/FLUX.2-dev-gguf. Load it with Unet Loader (GGUF) from the ComfyUI-GGUF node pack.
FP8 or Q8_0 for FLUX.2 dev on the RTX 4090 24 GB?
FP8 (35.5 GB): the RTX 4090 24 GB computes it natively, while Q8_0 (35.0 GB) is unpacked on the fly.
How much do I need to download for FLUX.2 dev on the RTX 4090 24 GB?
38.5 GB: flux2-dev-Q4_K_M.gguf, mistral_3_small_flux2_fp8.safetensors, flux2-vae.safetensors.