GPT-5.5 vs Claude Opus 4.8: The Complete 2026 Comparison

The most-watched matchup of the 2026 AI race is OpenAI's GPT-5.5 against Anthropic's Claude Opus 4.8. One wins on top-tier overall quality and a massive context window; the other on highly competitive output pricing and rock-solid coding ability. So which should you pick? This article runs a full head-to-head using live pricing data from llmprice.app.

Specs and pricing at a glance

Let's start with the numbers that matter. Prices below are in USD per million tokens (1M tokens); the quality score is a composite benchmark rating out of 100:

Price analysis: which is cheaper?

There's no single answer — it depends on your input-to-output ratio. GPT-5.5 charges just $5 for input but a steep $30 for output; Claude Opus 4.8 has pricier input ($10) but output is less than half the price ($12.50).

The dividing line: if your app generates a lot of text (long writing, code generation, multi-turn agent reasoning), output tokens dominate your bill and Claude Opus 4.8 is clearly cheaper. Conversely, if you read a lot of input and answer briefly (document Q&A, classification, summarization), GPT-5.5's low input price wins.

A concrete example: a request with 10K input and 2K output tokens costs about $0.11 on GPT-5.5 and $0.125 on Claude Opus 4.8 — nearly identical. But push output to 8K tokens and GPT-5.5 jumps to $0.29 while Claude stays at $0.20, and the gap widens. To run the math on your own scenario, use our cost calculator.

Quality and capabilities

On composite benchmarks, GPT-5.5 edges ahead at 97 vs Claude Opus 4.8's 94 — one of the highest-scoring models on the board. In practice both are "flagship" tier and the gap is rarely noticeable, but each has its strengths:

• GPT-5.5: the most complete on overall reasoning and multimodality (audio support), ideal for apps that take image or audio input.
• Claude Opus 4.8: long known for stable code quality and fewer hallucinations, a favorite of engineering teams and writing workflows.

Context window: GPT-5.5 dominates

This is the biggest hard-spec difference. GPT-5.5 offers up to 1,049K (~1.05 million) tokens of context — more than five times Claude Opus 4.8's 200K. If your task is "fit an entire codebase in one go," "analyze hundreds of pages of legal documents," or "hold a very long conversation in memory," GPT-5.5 is almost the only option. For most everyday apps, 200K is plenty and this edge may not matter.

Use-case recommendations

Conclusion and recommendation

There's no absolute winner, only the better fit for you. A simple rule:

• Need a huge context window or top overall quality → pick GPT-5.5.
• High output volume, want to cut costs, value coding → pick Claude Opus 4.8.

If you're budget-sensitive, don't forget both vendors have cheaper mid-tier models (GPT-5.4-mini, Claude Sonnet 4.6) that offer better value on many tasks. For a full side-by-side with live prices, see the homepage comparison covering all 30+ models.

Further reading: Cheapest LLM APIs in 2026 · How to Choose the Right AI Model