Claude Sonnet 4.5 vs GPT-5.1
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-5.1
59.6OpenAI · Nov 2025
A November 2025 update to GPT-5 with adaptive reasoning that spends thinking tokens only when a task needs them.
The verdict
Claude Sonnet 4.5 and GPT-5.1 split the 4 benchmarks they share evenly (2–2), so capability alone won't settle this one. GPT-5.1 is about 1.7x cheaper per blended million tokens (3:1 input:output mix). GPT-5.1 also takes 400K of context versus 200K for Claude Sonnet 4.5.
Benchmark head-to-head 2–2
Specs & pricing
| Claude Sonnet 4.5 | GPT-5.1 | |
|---|---|---|
| modhub Index | 65.5 | 59.6 |
| Input price / 1M | $3 | $1.25 |
| Output price / 1M | $15 | $10 |
| Context window | 200K | 400K |
| Max output | 64K | 128K |
| Open weights | no | no |
| Reasoning model | yes | yes |
| Multimodal input | text, image | text, image |
| Knowledge cutoff | Jan 2025 | Sep 2024 |
| Released | Sep 2025 | Nov 2025 |
| Example monthly cost* | $52.50 | $27.50 |
* 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-5.1?
- Claude Sonnet 4.5 and GPT-5.1 split the 4 benchmarks they share evenly (2–2), so capability alone won't settle this one. GPT-5.1 is about 1.7x cheaper per blended million tokens (3:1 input:output mix). GPT-5.1 also takes 400K of context versus 200K for Claude Sonnet 4.5.
- Which is cheaper, Claude Sonnet 4.5 or GPT-5.1?
- Claude Sonnet 4.5 costs $3/$15 per million input/output tokens, while GPT-5.1 costs $1.25/$10. For a typical workload of 10M input and 1.5M output tokens per month, that's $52.50 versus $27.50.
- Which model is better for coding, Claude Sonnet 4.5 or GPT-5.1?
- On SWE-bench Verified — the standard agentic-coding benchmark — Claude Sonnet 4.5 scores 77.2% versus 76.3% for GPT-5.1, making Claude Sonnet 4.5 the stronger pick for coding agents.