Gemma 4 31B IT on L20 48GB (48GB) — VRAM, KV Cache & Throughput
Gemma 4 31B IT (31.27B total, 31.27B active, Dense GQA) uses 17.07 GiB of 4-bit weights (Q4_K_M), requiring 19.04 GiB total at 8K context and 20.91 GiB at 32K on L20 48GB (~30 tok/s decode).
Fits with Safe Headroom
Measured GGUF shard size
HF config.json ↗
Required GPU Memory
19.04 GiB
20.44 GB (decimal)
Usable Hardware Memory
45.6 GiB
48 GB (physical)
Safe Headroom
+26.56 GiB
40% utilization
Est. Decode Throughput
~30 tok/s
31.27B active params
Est. Prefill Throughput
~998 tok/s
4K Prompt TTFT: ~4105 ms
Est. Cost / 1M Tokens
$1.75
Dense GQA · Apache-2.0
Recommended Hardware for Current Configuration
Best Single GPU
Arc Pro B60 24GB (24GB)
~$599
Best Value / Used GPU
RTX 3090 (24GB)
~$750
Apple Unified Memory
Ryzen AI Max+ 395 128GB
~$1,999
Cloud From
Vast.ai · $0.19 / hr
1x RTX 3090
Production Launch Commands
llama.cpp (GGUF)
llama-server -hf unsloth/gemma-4-31B-it-GGUF:Q4_K_M \ --ctx-size 8192 -ngl 999 --flash-attn
vLLM
vllm serve google/gemma-4-31B-it \ --max-model-len 8192 --gpu-memory-utilization 0.92
Live Token Speed Simulator (TTFT ~4105ms · ~30 tok/s)
[Gemma 4 31B IT · 19.04 GiB] allocated on target GPU. Prefill completed in TTFT window; streaming autoregressive tokens at memory-bandwidth-bound rate...
Cloud GPU Comparison & Rent-vs-Buy TCO
Verified public rates across RunPod, Vast.ai, Vultr, and DigitalOcean.
Purchase break-even
~26.6 months
Est. local power: $4.26 / mo
| Provider | Recommended Instance | Total VRAM | Hourly Rate | Monthly at Selected Hours | Billing Mode | Deploy |
|---|---|---|---|---|---|---|
| RunPod | 1x RTX 3090 (Community Cloud) | 24 GB | $0.22 / hr | $26.75 / mo | Per-second | Deploy GPU ↗ |
| Vast.ai | 1x RTX 3090 (Verified Host) | 24 GB | $0.19 / hr | $22.98 / mo | Spot / On-demand | Deploy GPU ↗ |
| Vultr ($300 Free Credit*) | 1x L40S 48GB (Dedicated Instance · $300 Credit*) | 48 GB | $1.67 / hr | $203.19 / mo | Hourly | Deploy GPU ↗ |
| Vultr Cloud GPU | 1x L40S 48GB (Dedicated Instance) | 48 GB | $1.67 / hr | $203.19 / mo | Hourly | Deploy GPU ↗ |
| DigitalOcean | 1x RTX 6000 Ada (Dedicated Instance) | 48 GB | $1.57 / hr | $190.91 / mo | Per-second | Deploy GPU ↗ |
Rates reflect public listings on the verification date and fluctuate with regional inventory.
Fine-Tuning VRAM Requirements (QLoRA / LoRA / Full) — Gemma 4 31B IT
QLoRA (4b)
Fits with Safe Headroom
22.57 GiB
Model Weights: 17.07 GiB · Gradients + Optimizer: 4.38 GiB · Act: 1.12 GiB
Recommended GPU: Radeon AI PRO R9700 32GB (32GB)
LoRA (16b)
Exceeds Available GPU Memory
66.61 GiB
Model Weights: 58.24 GiB · Gradients + Optimizer: 6.88 GiB · Act: 1.49 GiB
Recommended GPU: RTX PRO 6000 Blackwell (96GB)
Full BF16
Exceeds Available GPU Memory
241.4 GiB
Model Weights: 58.24 GiB · Gradients + Optimizer: 180.54 GiB · Act: 2.62 GiB
Recommended GPU: Instinct MI355X 288GB (288GB)
Engineering Sizing Notes & Optimization Playbook
Quick Hardware Verdict
L20 48GB (48GB physical, 45.6 GiB usable) runs 4-bit (Q4_K_M) Gemma 4 31B IT at 8K context using 19.04 GiB with 26.56 GiB of safe headroom (~30 tok/s single-stream decode).
KV Cache & Runtime Tuning
Gemma 4 31B IT uses Dense GQA (31.27B total, 31.27B active per token). Moving from 8K to 32K context expands FP16 KV cache from 1.41 GiB to 3.28 GiB; enabling 8-bit KV cache (llama.cpp -ctk q8_0 -ctv q8_0 or vLLM --kv-cache-dtype fp8) saves 1.64 GiB at 32K (reducing total VRAM to 19.27 GiB).
VRAM Scaling Across Context Windows (4K to 128K, 4-bit Weights)
Quantization Precision & Memory Matrix — Gemma 4 31B IT @ 8K
| Quantization Format | Weights (GiB) | KV Cache | Total VRAM (GiB) | Decode Speed | Compatibility (L20 48GB) | Recommended GPU | Data Source |
|---|---|---|---|---|---|---|---|
| Native Weights (BF16 / FP8 / MXFP4 — Lossless) (BF16) | 58.24 GiB | 1.41 GiB | 60.21 GiB (64.65 GB) | ~3.1 tok/s | Exceeds Available GPU Memory | RTX PRO 6000 Blackwell (96GB) | Official checkpoint size |
| FP8 / GGUF Q8_0 (8-bit — Near-Lossless) (Q8_0) | 30.94 GiB | 1.41 GiB | 32.91 GiB (35.34 GB) | ~16.9 tok/s | Fits with Safe Headroom | A40 48GB (48GB) | Config-derived formula |
| GGUF Q6_K (6-bit — High Precision) (Q6_K) | 23.47 GiB | 1.41 GiB | 25.44 GiB (27.32 GB) | ~22.1 tok/s | Fits with Safe Headroom | Radeon AI PRO R9700 32GB (32GB) | Measured GGUF shard size |
| GGUF Q5_K_M (5-bit — Balanced) (Q5_K_M) | 20.17 GiB | 1.41 GiB | 22.14 GiB (23.77 GB) | ~25.6 tok/s | Fits with Safe Headroom | Radeon AI PRO R9700 32GB (32GB) | Measured GGUF shard size |
| Q4_K_M / UD-Q4_K_XL / AWQ (4-bit — Recommended) (Q4_K_M) | 17.07 GiB | 1.41 GiB | 19.04 GiB (20.44 GB) | ~30 tok/s | Fits with Safe Headroom | Arc Pro B60 24GB (24GB) | Measured GGUF shard size |
| GGUF IQ4_XS (4.25-bit — Compact) (IQ4_XS) | 15.25 GiB | 1.41 GiB | 17.22 GiB (18.49 GB) | ~33.4 tok/s | Fits with Safe Headroom | Arc Pro B60 24GB (24GB) | Measured GGUF shard size |
| GGUF Q3_K_M (3-bit — Low VRAM) (Q3_K_M) | 13.72 GiB | 1.41 GiB | 15.69 GiB (16.85 GB) | ~36.9 tok/s | Fits with Safe Headroom | Arc Pro B60 24GB (24GB) | Measured GGUF shard size |
| GGUF UD-Q2_K_XL (2-bit — Extreme MoE) (UD-Q2_K_XL) | 10.97 GiB | 1.41 GiB | 12.94 GiB (13.89 GB) | ~45.6 tok/s | Fits with Safe Headroom | RTX 4060 Ti 16GB (16GB) | Measured GGUF shard size |
Technical Specifications & FAQ
Does Gemma 4 31B IT fit on L20 48GB (48GB)?
In 4-bit (Q4_K_M) at 8,192 context, Gemma 4 31B IT requires 19.04 GiB total GPU memory (17.07 GiB weights + 1.41 GiB KV cache + 0.56 GiB runtime buffers) against 45.6 GiB usable on L20 48GB, delivering ~30 tok/s decode.
How much VRAM does Gemma 4 31B IT need at 32K context?
At 32,768 context tokens, Gemma 4 31B IT (Dense GQA) allocates 3.28 GiB for KV cache and state, bringing total 4-bit VRAM to 20.91 GiB (22.45 GB decimal).
Evaluate This Model on Other GPUs
RTX 3060 12GB (12GB)RTX 4060 Ti 16GB (16GB)RTX 5060 Ti 16GB (16GB)RTX 4070 Ti Super (16GB)RTX 4080 Super (16GB)RTX 5070 12GB (12GB)RTX 5070 Ti (16GB)RTX 5080 (16GB)RTX 3090 (24GB)RTX 4090 (24GB)RTX 4090 D (24GB)RTX 5090 (32GB)RTX 5090 D (32GB)RTX A6000 (48GB)RTX 6000 Ada (48GB)RTX PRO 6000 Blackwell (96GB)DGX Spark (GB10 128GB) (128GB)L4 24GB (24GB)A40 48GB (48GB)L40S 48GB (48GB)A800 80GB SXM (80GB)A100 80GB SXM (80GB)H800 80GB SXM (80GB)H100 80GB SXM (80GB)H20 96GB HBM3 (96GB)H20 141GB HBM3e (141GB)H200 141GB SXM (141GB)B200 180GB (180GB)B300 288GB Blackwell Ultra (288GB)Ascend 910B 64GB (昇腾) (64GB)Ascend 910C 128GB (昇腾) (128GB)Atlas 300I Duo 96GB (310P) (96GB)MLU590 80GB (寒武纪思元) (80GB)DCU K100-AI 64GB (海光深算) (64GB)MetaX C500 64GB (沐曦曦云) (64GB)Kunlunxin P800 64GB (昆仑芯) (64GB)MTT S4000 48GB (摩尔线程) (48GB)Radeon RX 7900 XTX 24GB (24GB)Radeon AI PRO R9700 32GB (32GB)Ryzen AI Max+ 395 128GB (128GB)Instinct MI300X 192GB (192GB)Instinct MI325X 256GB (256GB)Instinct MI355X 288GB (288GB)Arc Pro B60 24GB (24GB)Gaudi 3 128GB HBM2e (128GB)Mac mini M4 Pro 64GB (64GB)MacBook Pro M4 Max 128GB (128GB)Mac Studio M4 Ultra 256GB (256GB)Mac Studio M3 Ultra 512GB (512GB)
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