Claude Sonnet 5.5 vs GPT-5.5 Instant
Claude Sonnet 5.5 leads the LLM Stats Score 58.0 to 32.2. Claude Sonnet 5.5 is 2.8x cheaper per token.
Anthropic · OpenAI · Updated for 2026
Which is better?
Claude Sonnet 5.5 leads the overall LLM Stats Score 58.0 to 32.2, ranking #3 overall.
In the 2 individual benchmarks reported for both models, Claude Sonnet 5.5 wins 2; this is a narrower head-to-head signal than the composite indexes.
On price, Claude Sonnet 5.5 is roughly 2.8x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Claude Sonnet 5.5 also accepts a larger context window (1,000,000 input tokens), making it the stronger choice for long documents and large codebases.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose Claude Sonnet 5.5
- overall performance matters — it scores 58.0 and ranks #3 on LLM Stats
- your work emphasizes reasoning — it leads those capability indexes
- you value its reported benchmark strengths — it wins 2 of 2 exact shared results
- cost matters — it's about 2.8x cheaper per token
- you process long inputs — it offers a 1,000,000 token context window
- you want the most recent training data — it shipped Sep 2026
Choose GPT-5.5 Instant
- you want predictable pricing at $5.00/M input and $30.00/M output
At a glance
The differences that matter most.
Capability indexes
Additional strengths measured across groups of related public benchmarks
Individual benchmarks
47 reported for Claude Sonnet 5.5 · 9 for GPT-5.5 Instant
Claude Sonnet 5.5 outperforms in 2 benchmarks (HealthBench, HealthBench Professional), while GPT-5.5 Instant is better at 0 benchmarks.
Claude Sonnet 5.5 significantly outperforms across most benchmarks.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Claude Sonnet 5.5 ($2.00/1M tokens) is 2.5x cheaper than GPT-5.5 Instant ($5.00/1M tokens).
For output processing, Claude Sonnet 5.5 ($10.00/1M tokens) is 3.0x cheaper than GPT-5.5 Instant ($30.00/1M tokens).
In conclusion, GPT-5.5 Instant is more expensive than Claude Sonnet 5.5.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Claude Sonnet 5.5 accepts 1,000,000 input tokens compared to GPT-5.5 Instant's 400,000 tokens. Both models can generate responses up to 128,000 tokens.
Input capabilities
Documented input modalities across available providers
Both Claude Sonnet 5.5 and GPT-5.5 Instant support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Claude Sonnet 5.5
GPT-5.5 Instant
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
Claude Sonnet 5.5 was released on 2026-09-28, while GPT-5.5 Instant was released on 2026-05-05.
Claude Sonnet 5.5 is 5 months newer than GPT-5.5 Instant.
Sep 28, 2026
6 days ago
4mo newerMay 5, 2026
5 months ago
Knowledge Cutoff
When training data ends
Claude Sonnet 5.5 has a knowledge cutoff of 2026-06-01, while GPT-5.5 Instant has a cutoff of 2025-08-31.
Claude Sonnet 5.5 has more recent training data (up to 2026-06-01), making it potentially better informed about events through that date compared to GPT-5.5 Instant (2025-08-31).
Jun 2026
10 mo newerAug 2025
Provider Availability
Claude Sonnet 5.5 is available from Anthropic. GPT-5.5 Instant is available from OpenAI.
Claude Sonnet 5.5
GPT-5.5 Instant
Outputs Comparison
Judge for yourself.
Run your own prompts against Claude Sonnet 5.5 and GPT-5.5 Instant side-by-side, then vote on the output you prefer.
FAQ
Common questions about Claude Sonnet 5.5 vs GPT-5.5 Instant.