o3 vs InternLM 2.5 20B

Compare o3 and InternLM 2.5 20B: pricing, performance, context window, latency, and best use cases. Side-by-side comparison on XALEN.

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

All OpenAI models All Shanghai AI Lab models What is an LLM API? Python Quickstart What is inference?
Feature o3 InternLM 2.5 20B
CategoryReasoningOpen Source
Parameters~1T20B
Context Window200K256K
Input Price$0.10/1M tokens$0.02/1M tokens
Output Price$0.40/1M tokens$0.04/1M tokens
Latency~2000ms~180ms

Choose o3 when:

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

Extended thinking, Complex logic, Mathematical reasoning

Choose InternLM 2.5 20B when:

  • ✓ Long context tasks
  • ✓ Research
  • ✓ Multilingual
Key Strengths:

256K context, Strong reasoning, Good multilingual

Verdict: o3 vs InternLM 2.5 20B

For cost efficiency, InternLM 2.5 20B wins at $0.02/1M input tokens. For speed, InternLM 2.5 20B is faster at ~180ms. o3 excels at Complex calculations while InternLM 2.5 20B is better for Long context 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. InternLM 2.5 20B costs $0.02 input and $0.04 output. InternLM 2.5 20B is 5.0x 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. InternLM 2.5 20B offers 256K context at ~180ms. InternLM 2.5 20B has the larger context window.

Best For

o3 (Reasoning) is optimized for: Complex calculations, Multi-factor analysis, Research-grade work. InternLM 2.5 20B (Open Source) works best for: Long context tasks, Research, Multilingual.

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 InternLM 2.5 20B
response_b = client.chat.completions.create(
    model="internlm-2-5-20b",
    messages=[{"role": "user", "content": "Your question here"}]
)

Start Building with XALEN

200+ AI models. One API. Pay-as-you-go.

Get API Key Try in Playground

Frequently Asked Questions

Which is better, o3 or InternLM 2.5 20B?

o3 (Reasoning, ~1T) offers Extended thinking. InternLM 2.5 20B (Open Source, 20B) offers 256K context. Choose o3 for Complex calculations or InternLM 2.5 20B for Long context tasks.

How much does o3 cost vs InternLM 2.5 20B?

o3: $0.10/1M input, $0.40/1M output. InternLM 2.5 20B: $0.02/1M input, $0.04/1M 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 InternLM 2.5 20B by changing the model parameter. No code changes needed.

Related Comparisons

o3 vs o3 Mini o3 vs o4-mini o3 vs Gemma 3 27B o3 vs Llama 4 Scout o3 vs Llama 4 Maverick o3 vs Llama 3.3 70B

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