Claude Sonnet 4.5 vs GPT-5.5
Benchmarks, API pricing and specs, head to head. Data updated 2026-06-10.
Claude Sonnet 4.5
65.5Anthropic · Sep 2025
The model that made 30-hour autonomous coding sessions real — 77.2% SWE-bench Verified and a 1M-token context beta at $3/$15.
GPT-5.5
77.2OpenAI · Apr 2026
OpenAI's flagship reasoning model with a 1M-token context window, built for hard coding, science and long-horizon agentic work.
The verdict
GPT-5.5 wins 4 of the 4 benchmarks these models share, against 0 for Claude Sonnet 4.5. Claude Sonnet 4.5 is about 1.9x cheaper per blended million tokens (3:1 input:output mix). GPT-5.5 also takes 1M of context versus 200K for Claude Sonnet 4.5.
Benchmark head-to-head 0–4
Specs & pricing
| Claude Sonnet 4.5 | GPT-5.5 | |
|---|---|---|
| modhub Index | 65.5 | 77.2 |
| Input price / 1M | $3 | $5 |
| Output price / 1M | $15 | $30 |
| Context window | 200K | 1M |
| Max output | 64K | 128K |
| Open weights | no | no |
| Reasoning model | yes | yes |
| Multimodal input | text, image | text, image |
| Knowledge cutoff | Jan 2025 | Jan 2026 |
| Released | Sep 2025 | Apr 2026 |
| Example monthly cost* | $52.50 | $95.00 |
* 10M input + 1.5M output tokens per month at list prices, no caching. Green = better value on that row.
Frequently asked questions
- Which is better, Claude Sonnet 4.5 or GPT-5.5?
- GPT-5.5 wins 4 of the 4 benchmarks these models share, against 0 for Claude Sonnet 4.5. Claude Sonnet 4.5 is about 1.9x cheaper per blended million tokens (3:1 input:output mix). GPT-5.5 also takes 1M of context versus 200K for Claude Sonnet 4.5.
- Which is cheaper, Claude Sonnet 4.5 or GPT-5.5?
- Claude Sonnet 4.5 costs $3/$15 per million input/output tokens, while GPT-5.5 costs $5/$30. For a typical workload of 10M input and 1.5M output tokens per month, that's $52.50 versus $95.00.
- Which model is better for coding, Claude Sonnet 4.5 or GPT-5.5?
- On SWE-bench Verified — the standard agentic-coding benchmark — GPT-5.5 scores 82.6% versus 77.2% for Claude Sonnet 4.5, making GPT-5.5 the stronger pick for coding agents.