Claude Opus 5 vs GPT-5.5: a data-driven comparison

Side-by-side comparison

Criterion	Claude Opus 5	GPT-5.5
Developer	Anthropic	OpenAI
Released	July 24, 2026	April 23, 2026
Capability index	92.7 / 100	89 / 100
Input price	$5	$5
Output price	$25	$30
Cost of a typical task	$0.15	$0.16
Context window	1,000,000 tokens	1,050,000 tokens
Maximum output	128,000 tokens	128,000 tokens
Reasoning mode	Yes	Yes
Tool calling	Yes	Yes
Accepted inputs	text, image, PDF	text, image, PDF
Open weights	No	No
Knowledge cutoff	May 2026	December 1, 2025

Two models head to head

This comparison pits two frontier models, the ones you pick when quality comes first against each other: Claude Opus 5 and GPT-5.5, one from Anthropic, the other from OpenAI. The first dates from July 24, 2026, the second from April 23, 2026.

All figures below come from public sources checked on October 22, 2026: models.dev and OpenRouter for prices and capabilities, Epoch AI for scores.

Performance

On our capability index, Claude Opus 5 scores 92.7 out of 100 and GPT-5.5 89. Claude Opus 5 leads by 3.7 points.

On the 5 benchmarks reported for both, Claude Opus 5 wins 3 times and GPT-5.5 2:

GPQA Diamond (PhD-level science questions): Claude Opus 5 93.9%, GPT-5.5 94%
OTIS Mock AIME (competition mathematics problems): Claude Opus 5 98.9%, GPT-5.5 100%
FrontierMath (very hard research-level mathematics): Claude Opus 5 85.6%, GPT-5.5 85.3%
FrontierCode (advanced programming tasks): Claude Opus 5 53.4%, GPT-5.5 43%
APEX-Agents (professional tasks carried out by an agent): Claude Opus 5 65.8%, GPT-5.5 55.1%

Budget

Claude Opus 5 costs $5 per million input tokens and $25 per million output tokens; GPT-5.5 costs $5 and $30.

For a typical agent task (read 20,000 tokens, write 2,000), expect $0.15 with Claude Opus 5 versus $0.16 with GPT-5.5. The cost is almost the same.

Run the numbers with your own volumes in the agent cost calculator.

Context and capabilities

GPT-5.5 reads more in one go: 1,050,000 tokens of context (roughly 1,575 pages), versus 1,000,000 for Claude Opus 5.

Reasoning mode: Claude Opus 5 yes, GPT-5.5 yes. Tool calling: Claude Opus 5 yes, GPT-5.5 yes. Image input: Claude Opus 5 yes, GPT-5.5 yes.

Neither publishes its weights: both are used through an API.

Knowledge cutoff: May 2026 for Claude Opus 5, December 1, 2025 for GPT-5.5.

In short

Our reading of the data:

Choose Claude Opus 5 for a higher capability index and a more recent release.

This verdict relies on public figures; it does not replace a trial on your own tasks.

Frequently asked questions

Claude Opus 5 or GPT-5.5: which is better?

On our index (Epoch AI data), Claude Opus 5 scores 92.7 and GPT-5.5 89 out of 100. The best choice also depends on price and on your use case.

Which one is cheaper?

Claude Opus 5. To read 20,000 tokens and write 2,000, expect $0.15 with Claude Opus 5 and $0.16 with GPT-5.5 (prices as of October 22, 2026).

Which one has the larger context window?

GPT-5.5, with 1,050,000 tokens versus 1,000,000.

Can I run Claude Opus 5 or GPT-5.5 on my own servers?

No: both are closed models, available through an API.

Claude Opus 5 or GPT-5.5: which to choose?