How much VRAM does Qwen3.5-27B need?

Q4_K_M is exactly 16,740,812,704 bytes (15.59 GiB) in weights. Add the KV cache, which depends on context length, plus roughly half a gigabyte of runtime overhead.

How large is Qwen3.5-27B's KV cache?

2.00 GiB at 32K context with an f16 cache, computed per layer from the model's architecture. Quantizing the cache to q8_0 roughly halves it.

Qwen · vision language

Qwen3.5-27B

Qwen/Qwen3.5-27B

Qwen3.5-27B at Q4_K_M is exactly 16,740,812,704 bytes (15.59 GiB / 16.74 GB) — an effective 4.821 bits per weight, not the nominal 4. Its KV cache at 32K is 2.00 GiB.

From the file· summed from 1 file(s)From the file· KV per layer

Parameters

27.8B

Architecture

qwen35

64 layers

Context

262,144

native (config.json)

License

apache-2.0

Shipped quantizations

● exact bytes, summed from published files

Quant	Size●	Exact bytes●	Effective bpw●	Tensors●	Publisher
UD-IQ2_XXS	7.98 GiB	8,573,593,504	2.469	—	unsloth
UD-IQ2_XXS	8.91 GiB	9,567,265,856	2.755	—	unsloth
IQ2_XXS	8.95 GiB	9,605,378,528	2.766	—	bartowski
UD-IQ2_M	9.49 GiB	10,188,072,864	2.934	—	unsloth
IQ2_XS	9.50 GiB	10,199,134,688	2.937	—	bartowski
IQ2_S	9.79 GiB	10,507,665,888	3.026	—	bartowski
UD-IQ2_M	10.27 GiB	11,023,557,696	3.174	—	unsloth
IQ2_M	10.32 GiB	11,085,693,408	3.192	—	bartowski
UD-IQ3_XXS	10.72 GiB	11,506,493,344	3.313	—	unsloth
Q2_K	11.22 GiB	12,051,775,968	3.470	—	bartowski
UD-IQ3_XXS	11.36 GiB	12,199,109,696	3.513	—	unsloth
Q3_K_S	11.45 GiB	12,289,423,264	3.539	—	unsloth
Q3_K_S	11.71 GiB	12,574,487,616	3.621	—	unsloth
IQ3_XXS	11.96 GiB	12,839,109,088	3.697	—	bartowski
Q2_K_L	12.38 GiB	13,293,375,968	3.828	—	bartowski
Q3_K_M	12.58 GiB	13,505,116,064	3.889	851	unsloth
IQ3_XS	12.61 GiB	13,542,740,448	3.900	—	bartowski
Q3_K_M	12.87 GiB	13,818,688,576	3.979	—	unsloth
Q3_K_S	12.98 GiB	13,932,679,648	4.012	—	bartowski
IQ3_M	13.15 GiB	14,115,852,768	4.065	—	bartowski
Q3_K_M	13.80 GiB	14,818,071,008	4.267	866	bartowski
IQ4_XS	13.95 GiB	14,977,484,704	4.313	851	unsloth
Q3_K_L	14.43 GiB	15,491,781,088	4.461	—	bartowski
IQ4_NL	14.61 GiB	15,687,894,944	4.518	—	unsloth
IQ4_XS	14.63 GiB	15,705,859,136	4.523	866	unsloth
Q4_0	14.64 GiB	15,721,973,664	4.527	—	unsloth
Q4_K_S	14.69 GiB	15,769,159,584	4.541	—	unsloth
IQ4_XS	14.70 GiB	15,780,159,968	4.544	—	bartowski
Q4_0	14.95 GiB	16,056,476,736	4.624	866	unsloth
Q4_K_S	15.01 GiB	16,121,357,376	4.642	—	unsloth
IQ4_NL	15.22 GiB	16,337,626,176	4.705	—	unsloth
IQ4_NL	15.40 GiB	16,538,165,728	4.762	—	bartowski
Q4_0	15.42 GiB	16,561,103,328	4.769	866	bartowski
Q4_K_M	15.59 GiB	16,740,812,704	4.821	851	unsloth
Q4_K_S	15.76 GiB	16,925,483,488	4.874	—	bartowski
Q4_K_M	15.93 GiB	17,106,773,056	4.926	866	unsloth
Q4_1	16.00 GiB	17,182,934,944	4.948	—	unsloth
Q4_1	16.34 GiB	17,540,703,296	5.051	—	unsloth
Q4_K_M	16.75 GiB	17,984,872,928	5.179	866	bartowski
Q4_1	16.80 GiB	18,037,793,248	5.194	—	bartowski

KV cache by context

computed per layer

Context	KV cache (f16)●	Flat formula	Overstated by	Full / windowed / recurrent
4,096	0.25 GiB	1.00 GiB	4.00×	16 / 0 / 48
8,192	0.50 GiB	2.00 GiB	4.00×	16 / 0 / 48
16,384	1.00 GiB	4.00 GiB	4.00×	16 / 0 / 48
32,768	2.00 GiB	8.00 GiB	4.00×	16 / 0 / 48
65,536	4.00 GiB	16.00 GiB	4.00×	16 / 0 / 48
131,072	8.00 GiB	32.00 GiB	4.00×	16 / 0 / 48

48 of 64 layers use linear attention, which keeps a fixed-size recurrent state instead of a per-token cache. Those layers do not grow with context at all — treating them as ordinary attention, as a flat formula does, overstates this model's cache by roughly 4.0× at long context.

Compare with

same modality, comparable size

vs Qwen3.6-35B-A3B vs Qwen3.6-27B-Fable-Fusion-711-Uncensored-Heretic-NM-DAU-MTP vs Qwen3.5-9B vs gemma-4-26B-A4B-it vs gemma-4-12B-it vs Qwen3.5-4B All alternatives →Will it fit on my card? →

Why other calculators give a different number

A parameters × bits ÷ 8 estimate puts Q4_K_M at roughly 14.55 GiB. The real file is 15.59 GiB, because a quantization is a mixture and some tensors are always kept at higher precision.

Architecture

from config.json

Layers

Attention heads

KV heads

Head dim

256

Hidden size

5120

Vocab

248,320

Sliding window

none

SWA period

—

MLA

Experts

—

Experts per token

—

use_sliding_window

—

Questions people ask

How much VRAM does Qwen3.5-27B need?: Q4_K_M is exactly 16,740,812,704 bytes (15.59 GiB) in weights. Add the KV cache, which depends on your context length, plus roughly half a gigabyte of runtime overhead.
How large is Qwen3.5-27B's KV cache?: 2.00 GiB at 32K context with an f16 cache, computed per layer. Quantizing the cache to q8_0 roughly halves it, which is often the difference between a context length fitting and not.
Which quantization of Qwen3.5-27B should I use?: Q4_K_M is the usual default. Pick the largest quantization that fits your card at the context you actually need — the table above gives exact sizes for every one published.