o3 vs Llama 3.1 405B

Compare o3 and Llama 3.1 405B: pricing, performance, context window, latency, and best use cases. Side-by-side comparison on XALEN.

Updated 2026-05-21 · By Abhishek Raj · Our methodology

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Feature o3 Llama 3.1 405B
CategoryReasoningOpen Source
Parameters~1T405B
Context Window200K128K
Input Price$0.10/1M tokens$0.08/1M tokens
Output Price$0.40/1M tokens$0.14/1M tokens
Latency~2000ms~600ms

Choose o3 when:

  • ✓ Complex calculations
  • ✓ Multi-factor analysis
  • ✓ Research-grade work
Key Strengths:

Extended thinking, Complex logic, Mathematical reasoning

Choose Llama 3.1 405B when:

  • ✓ Premium tasks
  • ✓ Research
  • ✓ Fine-tuning base
Key Strengths:

Largest open model, Highest open-source quality

Verdict: o3 vs Llama 3.1 405B

For cost efficiency, Llama 3.1 405B wins at $0.08/1M input tokens. For speed, o3 is faster at ~2000ms. o3 excels at Complex calculations while Llama 3.1 405B is better for Premium tasks. Both are available on XALEN through a single API — try them in the Playground to see which fits your workload.

Detailed Analysis

Pricing Comparison

o3 costs $0.10/1M input tokens and $0.40/1M output tokens. Llama 3.1 405B costs $0.08 input and $0.14 output. Llama 3.1 405B is 1.3x cheaper on input tokens. XALEN offers batch processing at 50% discount on both models.

Performance & Context

o3 has a 200K context window with ~2000ms latency. Llama 3.1 405B offers 128K context at ~600ms. o3 has the larger context window.

Best For

o3 (Reasoning) is optimized for: Complex calculations, Multi-factor analysis, Research-grade work. Llama 3.1 405B (Open Source) works best for: Premium tasks, Research, Fine-tuning base.

Try Both on XALEN

Both models are available through XALEN's OpenAI-compatible API. Switch between them by changing the model parameter:

from xalen import XALEN

client = XALEN(api_key="xln_test_YOUR_KEY")

# Use o3
response_a = client.chat.completions.create(
    model="o3",
    messages=[{"role": "user", "content": "Your question here"}]
)

# Use Llama 3.1 405B
response_b = client.chat.completions.create(
    model="llama-3-1-405b",
    messages=[{"role": "user", "content": "Your question here"}]
)

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Get API Key Try in Playground

Frequently Asked Questions

Which is better, o3 or Llama 3.1 405B?

o3 (Reasoning, ~1T) offers Extended thinking. Llama 3.1 405B (Open Source, 405B) offers Largest open model. Choose o3 for Complex calculations or Llama 3.1 405B for Premium tasks.

How much does o3 cost vs Llama 3.1 405B?

o3: $0.10/1M input, $0.40/1M output. Llama 3.1 405B: $0.08/1M input, $0.14/1M output. Both available on XALEN with batch processing at 50% discount.

Can I use both models on XALEN?

Yes. XALEN provides 200+ models through a single OpenAI-compatible API. Switch between o3 and Llama 3.1 405B by changing the model parameter. No code changes needed.

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Last updated: 2026-05-21. Pricing and specifications may change. Check pricing page for latest rates.