Anthropic · Released Sep 29, 2025Claude Sonnet 4.5
Balanced Claude model for coding, analysis, agent workflows, and cost control.
- Capability
- 146.8ECI · #64 of 148
- Input
- $3.00per 1M tokens
- Output
- $15.00per 1M tokens
- Context
- 200K64K max output
What it costs
- Input
- $3.00per million tokens
- Output
- $15.00per million tokens
- Cached input
- $0.30per million tokens
- Cache write
- $3.75per million tokens
- Blended (3:1)
- $6.00pricier than 90% of priced models
Typical monthly bills
| Monthly usage | Estimated cost |
|---|---|
| Side project2M input + 0.5M output tokens | $13.50 |
| Team assistant25M input + 5M output tokens | $150.00 |
| Production app250M input + 50M output tokens | $1,500 |
Official Anthropic API price, as listed on models.dev.
Independent benchmarks
#64 of 148 scored models
The shaded band is Epoch AI’s confidence range (145.3–148.5); the tick marks the median scored model.
Scores from Epoch AI, run independently of Anthropic.
The details
- Lab
- Anthropic
- Released
- Sep 29, 2025
- Knowledge cutoff
- Jul 31, 2025
- Context window
- 200,000 tokens
- Max output
- 64,000 tokens
- Inputs
- Text, Images, PDFs
- Output
- Text
- Reasoning
- Thinking budget
- Tool calling
- Yes
- Structured output
- Yes
- Weights
- Proprietary
- API model ID
claude-sonnet-4-5on Anthropic- Availability
- 28 API providerslisted on models.dev
What Anthropic claims
Published by the lab at launch. Settings vary, so compare these only with care.
| Benchmark | Score | Setting | Source |
|---|---|---|---|
| SWE-Bench Pro | 43.6 resolve rate | — | Source |
More from Anthropic
About Claude Sonnet 4.5
How much does Claude Sonnet 4.5 cost?
Claude Sonnet 4.5 costs $3.00 input / $15.00 output per million tokens (official Anthropic API price). Cached input is $0.30 per million tokens, and writing to the cache costs $3.75. At a 3:1 input-to-output mix that is $6.00 per million tokens, more expensive than 90% of the 360 priced models we track.
What is the context window of Claude Sonnet 4.5?
Claude Sonnet 4.5 accepts up to 200,000 tokens per request and can write up to 64,000 tokens in one response.
How good is Claude Sonnet 4.5?
Epoch AI gives Claude Sonnet 4.5 a Capabilities Index score of 146.8 (likely range 145.3–148.5), ranking it #64 of 148 models Epoch has scored. Epoch AI benchmark results: GPQA Diamond 82.3%, FrontierMath Tiers 1–3 23.9%, OTIS Mock AIME 2024–2025 77.8%, SWE-bench Verified 71.3%, SimpleQA Verified 30.7%.
Is Claude Sonnet 4.5 open source?
No. Claude Sonnet 4.5 is proprietary; you use it through Anthropic’s API or partner platforms.
What inputs does Claude Sonnet 4.5 support?
Claude Sonnet 4.5 accepts text, images and PDFs and replies in text. It is a reasoning model, supports tool calling and can return structured JSON output.
When was Claude Sonnet 4.5 released?
Anthropic released Claude Sonnet 4.5 on Sep 29, 2025. Its training data runs to Jul 31, 2025.
What are the best alternatives to Claude Sonnet 4.5?
The closest current models from other labs on capability, price and release date are o3 (OpenAI, ECI 146.9, $2.00 / $8.00), Gemini 2.5 Pro (Google, ECI 145.3, $1.25 / $10.00), Inkling (Thinking Machines, ECI 148.6, $3.74 / $9.36) and Qwen3 Max (Alibaba (Qwen), ECI 142.4, $1.20 / $6.00).