Qwen 3.5 27B
By Alibaba · China
Updated 2026-07-13
Overview
Alibaba's dense 27B Qwen 3.5 with a 262K context window and calibrated thinking mode. One of the best quality-to-size trade-offs in the open 25B-30B class.
When to pick this model
- Math, science, and STEM-heavy reasoning
- Long-context analysis at 100K+ tokens
- Single high-end GPU production deployments
- Multilingual technical workloads
- Replacing closed mid-tier APIs
VRAM requirements by quantization
| Quantization | VRAM required |
|---|---|
| Q4_K_M (recommended) | 16 GB |
| Q5_K_M | 19 GB |
| Q8_0 | 29 GB |
| FP16 (no quantization) | 54 GB |
VRAM figures include model weights plus a typical 8k KV cache and ~600 MB runtime overhead (Ollama / llama.cpp baseline). Add headroom for higher context lengths.
In practice, Qwen 3.5 27B needs a 16 GB card at Q4_K_M (16 GB). Stepping up to Q8_0 nearly doubles the footprint to 29 GB, and unquantized FP16 weights take 54 GB — plan your GPU around the Q4 or Q5 figure unless you specifically need the higher fidelity.
Without a GPU, Qwen 3.5 27B needs roughly 28 GB of system RAM to run on CPU via llama.cpp or Ollama — workable for background jobs, but far slower than GPU inference. Throughput estimates from our compatibility engine: around 3 tokens/sec on entry-level GPUs, on the order of 13 tokens/sec on a mid-range card, and up to 32 tokens/sec on high-end hardware — assuming the chosen quantization fully fits in VRAM.
What hardware do you need
The table below matches Qwen 3.5 27B to common GPU memory tiers, using the highest-fidelity quantization that fully fits each card class. Spilling layers to system RAM works but costs most of the speed, so size your card to the quantization you actually want to run.
| GPU memory | Example cards | Best fit for Qwen 3.5 27B |
|---|---|---|
| 8 GB | RTX 5070 Laptop, RTX 5060, RTX 5060 Ti 8GB | Does not fit — needs 16 GB at Q4_K_M |
| 12 GB | RTX 5070, RTX 5070 Ti Laptop, RTX 4080 Laptop | Does not fit — needs 16 GB at Q4_K_M |
| 16 GB | RTX 5080, RTX 4080 Super, Radeon RX 9070 XT | Q4_K_M (16 GB used) |
| 24 GB | RTX 4090, Radeon RX 7900 XTX, RTX 5090 Laptop | Q5_K_M (19 GB used) |
| 32 GB | RTX 5090 | Q8_0 (29 GB used) |
Which GPU should you buy to run Qwen 3.5 27B?
To run Qwen 3.5 27B locally at Q4, you need ~16 GB of VRAM. The best value for this is a RTX 5070 Ti (16 GB VRAM).
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Strengths
- 262K native context window
- Well-calibrated thinking mode
- Strong math and science reasoning
- Apache 2.0 license
Limitations
- Needs ~16GB VRAM in Q4
- Gemma 3 27B is a close competitor
- Thinking mode adds latency on simple queries
Typical workloads
In our catalog grid, Qwen 3.5 27B is filed under Pro Writing, Reasoning, Multilingual — the use cases where its size/quality trade-off makes the most sense. Its tags translate to concrete workloads: multi-step reasoning and math-flavoured tasks; multilingual workloads.
The 255k-token context window is large enough to hold entire codebases' worth of files or long reports in a single prompt, which is what makes local RAG and document analysis practical. The Apache 2.0 license is permissive, so shipping it inside a commercial product raises no special legal questions.
Architecture & training
Architecture: Dense · 27B · Qwen 3.5 · hybrid thinking · 262k native context
Training: Enriched Qwen 3.5 corpus, strong in complex reasoning with long context.
The best Apache-licensed dense model in the 27B class for long-context reasoning.
Quick start
ollama run qwen3.5:27bOr use the open-source MCP server to query this model from Claude Desktop, Cursor, or any MCP-compatible client.
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Frequently asked questions
How much VRAM does Qwen 3.5 27B need?
At the recommended Q4_K_M quantization, Qwen 3.5 27B needs about 16 GB of VRAM. Q8_0 takes 29 GB, and unquantized FP16 weights take 54 GB.
Can Qwen 3.5 27B run without a GPU?
Yes — with roughly 28 GB of system RAM it runs CPU-only through llama.cpp or Ollama. Expect a fraction of GPU speed, which is fine for background or batch jobs but slow for interactive chat.
What context window does Qwen 3.5 27B support?
Qwen 3.5 27B supports a 255k-token context window (262,000 tokens).
Can I use Qwen 3.5 27B commercially?
Yes. Qwen 3.5 27B is released under Apache 2.0, a permissive open-source license that allows commercial use, modification and redistribution.
How fast is Qwen 3.5 27B on consumer hardware?
Our compatibility engine estimates on the order of 13 tokens/sec on a mid-range GPU and up to 32 tokens/sec on high-end cards, assuming the quantization fully fits in VRAM.
Which quantization of Qwen 3.5 27B should I download first?
Start with Q4_K_M (16 GB) — the standard size/quality sweet spot. Step up to Q5_K_M or Q8_0 only if you have VRAM headroom. On a 24 GB card you can run up to Q5_K_M.