Can GPT-OSS 20B run on NVIDIA A40 48GB?

YES — Runs Great

S90Excellent

Estimated from fit model

GPT-OSS 20B needs ~21.3 GB VRAM. NVIDIA A40 48GB has 48.0 GB. With Q4_K_M quantization, expect ~97 tok/s.

Runtime: OllamaCapacity: RoomyBandwidth: MediumStack: BasicBottleneck: Balanced

Operating mode

Choose the run profile you care about

Interactive favors responsiveness, while light API and scale-out lean harder on serving readiness. The fit stays the same, but the recommendation lens changes.

Current mode

Balanced

Balanced for general local use. Keeps the ranking neutral across personal and serving workflows.

Capabilities:

Select quantization to explore

Q4_K_M (Medium quality) — 21.3 GB, 104.2 tok/s, Runs well

21.3 GB required48.0 GB available

44% VRAM used

Fit status

Runs well

Decode

104.2 tok/s

TTFT

1858 ms

Safe context

128K

Memory

21.3 GB / 48.0 GB

Memory breakdown

Weights12.8 GB

KV Cache2.4 GB

Runtime1.2 GB

Headroom4.8 GB

See how fast it feels

See how fast it feelsGPT-OSS 20B on NVIDIA A40 48GB
1st promptCold start — includes initialization
>Write a Python function to sort a list
Here's a Python function that sorts a list using quicksort:

def quicksort(arr):
    if len(arr) <= 1:
        return arr
    pivot = arr[len(arr) // 2]
    left   = [x for x in arr if x < pivot]
    middle = [x for x in arr if x == pivot]
    right  = [x for x in arr if x > pivot]
    return quicksort(left) + middle + quicksort(right)

# Example usage
numbers = [3, 6, 8, 10, 1, 2, 1]
print(quicksort(numbers))  # [1, 1, 2, 3, 6, 8, 10]

The algorithm picks a pivot, partitions the list into smaller, equal, and larger elements, then recursively sorts each partition and concatenates the results.
2nd promptWarm — model ready, no init overhead
>Now add type hints and a docstring
def quicksort(arr: list[int]) -> list[int]:
    """Sort a list using the quicksort algorithm.

    Args:
        arr: List of integers to sort.

    Returns:
        A new sorted list.
    """
    if len(arr) <= 1:
        return arr
    pivot = arr[len(arr) // 2]
    left   = [x for x in arr if x < pivot]
    middle = [x for x in arr if x == pivot]
    right  = [x for x in arr if x > pivot]
    return quicksort(left) + middle + quicksort(right)

Added type hints for the input and return type, plus a Google-style docstring.
Estimated: 104.2 tok/s decode · 1.9s TTFT (warm) · 261 tok/s prefill

What limits this setup

This setup is broadly balanced for this model.

No major red flags

This recommendation has enough memory headroom and acceptable estimated speed for the selected workload.

Best improvement path

Performance by workload

Workload	Grade	Fit	Decode	TTFT	Context
Chat	S	Runs well	96.9 tok/s	1089 ms	128K
Coding	S	Runs well	96.9 tok/s	1997 ms	128K
Agentic Coding	S	Runs well	96.9 tok/s	2905 ms	128K
Reasoning	S	Runs well	96.9 tok/s	2360 ms	128K
RAG	S	Runs well	96.9 tok/s	3631 ms	128K

Quantization options

How GPT-OSS 20B (21B params) fits at each quantization level on NVIDIA A40 48GB (48.0 GB usable).

Quant	Bits	VRAM	Quality	Fit
Q2_K	2	8.2 GB	Low	A81
Q3_K_S	3	10.3 GB	Low	A82
NVFP4	4	11.8 GB	Medium	A82
Q4_K_M	4	12.8 GB	Medium	A82
Q5_K_M	5	15.1 GB	High	A83
Q6_K	6	17.2 GB	High	A84
Q8_0Best for your GPU	8	22.5 GB	Very High	S85
F16	16	43.1 GB	Maximum	F0

Get started

Copy-paste commands to run GPT-OSS 20B on your machine.

Run

ollama run gpt-oss

Your hardware

More models your NVIDIA A40 48GB can run

Model	Params	Grade	Decode
Qwen3-Coder 30B A3B Instruct	30.5B	S	82.1 tok/s
Qwen 3.5 27B	27B	S	35.6 tok/s
Qwen 3.6 27B	27B	S	35.7 tok/s
Qwen 3.6 35B A3B	35B	S	69 tok/s
Qwen3-VL 30B A3B Instruct	30B	S	84.9 tok/s

Frequently asked questions

Can NVIDIA A40 48GB run GPT-OSS 20B?

Yes, NVIDIA A40 48GB can run GPT-OSS 20B with a S grade (Runs well). Expected decode speed: 96.9 tok/s.

How much VRAM does GPT-OSS 20B need?

GPT-OSS 20B (21B parameters) requires approximately 21.3 GB of memory with Q4_K_M quantization.

What is the best quantization for GPT-OSS 20B?

The recommended quantization for GPT-OSS 20B is Q4_K_M, which balances quality and memory efficiency.

What speed will GPT-OSS 20B run at on NVIDIA A40 48GB?

On NVIDIA A40 48GB, GPT-OSS 20B achieves approximately 96.9 tokens per second decode speed with a time-to-first-token of 1997ms using Q4_K_M quantization.

Can NVIDIA A40 48GB run GPT-OSS 20B for coding?

For coding workloads, GPT-OSS 20B on NVIDIA A40 48GB receives a S grade with 96.9 tok/s and 128K context.

What context window can GPT-OSS 20B use on NVIDIA A40 48GB?

On NVIDIA A40 48GB, GPT-OSS 20B can safely use up to 128K tokens of context. The model's official context limit is 128K, but available memory constrains the safe maximum.

See all results for NVIDIA A40 48GB See all hardware for GPT-OSS 20B

Embed this result▼

Paste this snippet into any page to show a live fit card.

<iframe src="https://willitrunai.com/embed/gpt-oss-20b-on-a40-48gb" width="400" height="180" frameborder="0" style="border:none;border-radius:12px;overflow:hidden;" title="Will It Run AI — fit result"></iframe>

Preview: