Short answer: use 4GB only for a constrained Q4 workload, 6GB as the practical Q4 tier, 8GB as a bounded Q8 target, and 12GB for the official 8.876GB BF16 checkpoint. Every official GGUF deployment also needs a separate multimodal projector.
Do not count only the language file. Qwen’s official Q4_K_M file is 2.497GB, but the complete path is 2.951GB with the Q8_0 projector or 3.333GB with the F16 projector. Then reserve cache, image/video state, runtime buffers and display use.
Qwen3-VL 4B files and practical tiers
| Official deployment path | Displayed files | Combined file size | Planning tier |
|---|---|---|---|
| Q4_K_M + Q8 projector | 2.497GB + 0.454GB | 2.951GB | 4GB constrained; 6GB practical |
| Q4_K_M + F16 projector | 2.497GB + 0.836GB | 3.333GB | 4GB very tight; 6GB practical |
| Q8_0 + Q8 projector | 4.280GB + 0.454GB | 4.734GB | 6GB bounded; 8GB practical |
| Q8_0 + F16 projector | 4.280GB + 0.836GB | 5.117GB | 6GB tight; 8GB practical |
| Official BF16 safetensors | 2 shards totaling 8.876GB | 8.876GB | 12GB bounded; 16GB safer |
Why 4GB is constrained
The smallest complete official pair occupies 2.951GB before cache or runtime state. The illustrative FP16/BF16 language cache is another 1.125GiB at an 8K allocation, already exceeding 4GB when simply added to the files. Cache quantization, a shorter allocation or partial offload can change device use, but 4GB is not a roomy full-offload target.
Six gigabytes is the practical Q4 tier and a bounded Q8 target. Eight gigabytes gives the complete Q8 pair useful room. The official BF16 weights already occupy 8.876GB before cache and vision processing, making 12GB a bounded target and 16GB safer.
KV cache: 144KiB per allocated text token
Qwen’s official 4B configuration lists 36 language layers, eight KV heads and a 128-element head dimension. With FP16/BF16 keys and values, one sequence uses 2 × 36 × 8 × 128 × 2 = 147,456 bytes, or 144KiB per allocated text token.
| Allocated text tokens | FP16/BF16 KV payload |
|---|---|
| 4K | 0.5625GiB |
| 8K | 1.125GiB |
| 32K | 4.5GiB |
| 64K | 9GiB |
| 256K architectural maximum | 36GiB |
Native 256K context is an architectural maximum, not a promise that this allocation fits on compact hardware. The illustrative cache payload alone is 36GiB at 256K.
Vision memory depends on the workload
- Images: dimensions and image count change visual-token volume.
- Video: sampled frames, duration, resolution and timestamp processing change work and memory.
- DeepStack: the configuration fuses intermediate vision features from layers 5, 11 and 17.
- Projector precision: the official Q8_0 and F16 projectors differ by about 382MB.
- Concurrency: parallel requests multiply request-specific cache and intermediate allocations.
- Runtime: verify the exact Transformers, vLLM, SGLang, llama.cpp or application version and prove the image/video path works.
Qwen3-VL 4B versus 8B
Both official configurations have 36 language layers, eight KV heads and the same 144KiB-per-token FP16/BF16 language-cache geometry. Their complete Q4 paths differ substantially: 2.951GB for 4B and 5.780GB for 8B with the Q8_0 projector. Equal cache geometry does not imply equal weights, speed, output quality or task accuracy.
Compare the Qwen3-VL family hub, Qwen3-VL 8B guide, Qwen2.5-VL 3B guide and cross-family multimodal guide.
Reproducible Qwen3-VL 4B fit test
- Record the exact repository, revision, Instruct/Thinking variant, language file, projector and checksums.
- Record runtime/version and verify Qwen3-VL image and video support.
- Record model, projector and cache precision plus every device placement or offload.
- Fix image dimensions/count, video sampling, text allocation, output target and concurrency.
- Measure accelerator and system memory before load, after load, after vision encoding and at peak generation.
- Use image-grounded and video-grounded prompts; text output alone does not prove modality support.
- Capture preprocessing time, time to first token, throughput, fallback and errors.
Use the 3B/4B sizing guide, 8GB–16GB capacity comparison, VRAM calculator, workload test and benchmark submission.
Continue planning
Browse all guides and tools. Capacity fit does not establish speed, visual accuracy or output quality.
Smaller model: the Qwen3-VL 2B VRAM guide covers official complete Q4/Q8 projector paths and 112KiB-per-token cache geometry.
Sources and limits
- Qwen official Qwen3-VL 4B repository
- Qwen official configuration
- Qwen official BF16 index
- Qwen official GGUF repository
- Qwen3-VL official code repository
- HighVRAM methodology
Reviewed October 25, 2026. Artifact sizes and architecture fields were read from official Qwen repositories. HighVRAM has not independently benchmarked every runtime, image/video workload, variant or quantization. File size is not peak resident memory.
Hybrid successor comparison: Qwen3.5-4B uses a 3:1 linear/full-attention stack and community GGUF provenance, so its cache and artifact assumptions differ from Qwen3-VL 4B.