How much VRAM does Qwen3-Reranker-4B need?

Q4_K_M is exactly 2,496,713,696 bytes (2.33 GiB) in weights. Add the KV cache, which depends on context length, plus roughly half a gigabyte of runtime overhead.

How large is Qwen3-Reranker-4B's KV cache?

4.50 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 · text

Qwen3-Reranker-4B

Qwen/Qwen3-Reranker-4B

Qwen3-Reranker-4B at Q4_K_M is exactly 2,496,713,696 bytes (2.33 GiB / 2.50 GB) — an effective 4.966 bits per weight, not the nominal 4. Its KV cache at 32K is 4.50 GiB.

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

Parameters

4.0B

Architecture

qwen3

36 layers

Context

40,960

native (config.json)

License

apache-2.0

Shipped quantizations

● exact bytes, summed from published files

Quant	Size●	Exact bytes●	Effective bpw●	Tensors●	Publisher
Q2_K	1.55 GiB	1,668,932,576	3.320	—	DevQuasar
Q2_K	1.55 GiB	1,668,933,024	3.320	—	mradermacher
Q2_K	1.55 GiB	1,668,935,136	3.320	—	Voodisss
Q3_K_S	1.76 GiB	1,886,430,176	3.752	—	DevQuasar
Q3_K_S	1.76 GiB	1,886,430,624	3.752	—	mradermacher
Q3_K_M	1.93 GiB	2,075,050,976	4.128	—	DevQuasar
Q3_K_M	1.93 GiB	2,075,051,424	4.128	—	mradermacher
Q3_K_M	1.93 GiB	2,075,054,048	4.128	—	Voodisss
Q3_K_L	2.09 GiB	2,239,218,656	4.454	—	DevQuasar
Q3_K_L	2.09 GiB	2,239,219,104	4.454	—	mradermacher
IQ4_XS	2.13 GiB	2,285,749,664	4.547	—	mradermacher
Q4_0	2.21 GiB	2,368,983,680	4.712	—	Voodisss
Q4_K_S	2.22 GiB	2,382,742,496	4.740	—	DevQuasar
Q4_K_S	2.22 GiB	2,382,742,944	4.740	—	mradermacher
Q4_K_M	2.33 GiB	2,496,713,696	4.966	—	DevQuasar
Q4_K_M	2.33 GiB	2,496,714,144	4.966	—	mradermacher
Q4_K_M	2.33 GiB	2,496,717,440	4.966	—	Voodisss
Q5_K_S	2.63 GiB	2,823,144,416	5.616	—	DevQuasar
Q5_K_S	2.63 GiB	2,823,144,864	5.616	—	mradermacher
Q5_0	2.63 GiB	2,823,148,800	5.616	—	Voodisss
Q5_K_M	2.69 GiB	2,888,946,656	5.747	—	DevQuasar
Q5_K_M	2.69 GiB	2,888,947,104	5.747	—	mradermacher
Q5_K_M	2.69 GiB	2,888,951,040	5.747	—	Voodisss
Q6_K	3.08 GiB	3,305,694,176	6.576	—	DevQuasar
Q6_K	3.08 GiB	3,305,694,624	6.576	—	mradermacher
Q6_K	3.08 GiB	3,305,699,264	6.576	—	Voodisss
Q8_0	3.99 GiB	4,279,672,608	8.513	—	DevQuasar
Q8_0	3.99 GiB	4,279,673,056	8.513	—	mradermacher
Q8_0	3.99 GiB	4,279,678,912	8.513	—	Voodisss
F16	7.50 GiB	8,049,911,808	16.013	—	DevQuasar
F16	7.50 GiB	8,049,912,256	16.013	—	mradermacher
F16	7.50 GiB	8,049,922,912	16.013	—	Voodisss

KV cache by context

computed per layer

Context	KV cache (f16)●	Flat formula	Overstated by	Full / windowed / recurrent
4,096	0.56 GiB	0.56 GiB	—	36 / 0 / 0
8,192	1.13 GiB	1.13 GiB	—	36 / 0 / 0
16,384	2.25 GiB	2.25 GiB	—	36 / 0 / 0
32,768	4.50 GiB	4.50 GiB	—	36 / 0 / 0
65,536	9.00 GiB	9.00 GiB	—	36 / 0 / 0
131,072	18.00 GiB	18.00 GiB	—	36 / 0 / 0

Compare with

same modality, comparable size

vs gemma-4-E4B-it vs Qwen3-4B vs Qwen3-8B vs HyperCLOVAX-SEED-Text-Instruct-1.5B vs Llama-3.2-1B-Instruct vs Qwen3-VL-8B-Instruct-abliterated-v1 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 2.11 GiB. The real file is 2.33 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

128

Hidden size

2560

Vocab

151,669

Sliding window

none

SWA period

—

MLA

Experts

—

Experts per token

—

use_sliding_window

false

Questions people ask

How much VRAM does Qwen3-Reranker-4B need?: Q4_K_M is exactly 2,496,713,696 bytes (2.33 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-Reranker-4B's KV cache?: 4.50 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-Reranker-4B 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.