Which is cheaper, GPT-5.5 and Grok 4.5?

Grok 4.5 has the lowest input price. Per 1M input tokens: GPT-5.5 from $5.00 and Grok 4.5 from $2.00.

Which has the larger context window, GPT-5.5 and Grok 4.5?

GPT-5.5 has the largest context window: GPT-5.5 1,050,000 tokens and Grok 4.5 500,000 tokens.

Which is better for coding, GPT-5.5 and Grok 4.5?

GPT-5.5 scores highest on the Artificial Analysis Coding Index: GPT-5.5 74.9 and Grok 4.5 72.4.

Which is faster, GPT-5.5 and Grok 4.5?

Grok 4.5 has the highest median throughput on FastRouter: GPT-5.5 <1 t/s and Grok 4.5 <1 t/s.

Can I switch between GPT-5.5 and Grok 4.5 without changing my code?

Yes. All of them are served through FastRouter's OpenAI-compatible API, so switching is a change of the model parameter (openai/gpt-5.5, x-ai/grok-4.5).

GPT-5.5 vs Grok 4.5

Side-by-side pricing per provider, context window, benchmark scores and speed, all on one OpenAI-compatible API.

GPT-5.5 OpenAIopenai/gpt-5.5

Grok 4.5 xAIx-ai/grok-4.5

Creator

OpenAI

xAI

Released

Apr 24, 2026

Jul 8, 2026

Context window

1.05M

500K

Max output

128K

500K

Input / 1MLowest provider price

$5.00$5.00–$5.50 across 2

$2.00

Output / 1MLowest provider price

$30.00$30.00–$33.00 across 2

$6.00

Providers

IntelligenceArtificial Analysis index

38.4

38.8

CodingArtificial Analysis index

74.9

72.4

LatencyMedian time to first token

6.1s

81s

ThroughputMedian tokens per second

<1 t/s

Accepts

Files, Image, Text

Text, Image

Produces

Text

Tool calling

Yes

Structured output

Yes

Reasoning

Yes

GPT-5.5 vs Grok 4.5: summary

GPT-5.5 and Grok 4.5 are both available through FastRouter's OpenAI-compatible API, so switching between them is a change of model id, not a new integration.

GPT-5.5, from OpenAI, has a 1,050,000-token context window, costs from $5.00/1M input and $30.00/1M output tokens across 2 providers and scores 38.4 on the Artificial Analysis Intelligence Index.

Grok 4.5, from xAI, has a 500,000-token context window, costs $2.00/1M input and $6.00/1M output tokens and scores 38.8 on the Artificial Analysis Intelligence Index.

Grok 4.5 is the cheapest on input, 2.5× cheaper than the next model, GPT-5.5 has the largest context window, Grok 4.5 scores highest for intelligence, GPT-5.5 leads on coding and Grok 4.5 has the highest throughput.

Switch with one line

client = OpenAI(base_url="https://api.fastrouter.ai/api/v1", api_key="<FASTROUTER_API_KEY>") client.chat.completions.create(model="openai/gpt-5.5", messages=[...]) # or client.chat.completions.create(model="x-ai/grok-4.5", messages=[...])

Full API docs

Frequently asked questions

More comparisons

Benchmark scores sourced from ArtificialAnalysis