Anthropic · Released Sep 28, 2026Claude Sonnet 5.5
Fast Claude model for everyday coding, agents, and knowledge work.
- Capability
- 165.2ECI · #3 of 148
- Input
- $2.00per 1M tokens
- Output
- $10.00per 1M tokens
- Context
- 1M128K max output
What it costs
- Input
- $2.00per million tokens
- Output
- $10.00per million tokens
- Cached input
- $0.20per million tokens
- Cache write
- $2.50per million tokens
- Blended (3:1)
- $4.00pricier than 83% of priced models
Typical monthly bills
| Monthly usage | Estimated cost |
|---|---|
| Side project2M input + 0.5M output tokens | $9.00 |
| Team assistant25M input + 5M output tokens | $100.00 |
| Production app250M input + 50M output tokens | $1,000 |
Official Anthropic API price, as listed on models.dev.
Independent benchmarks
#3 of 148 scored models
The shaded band is Epoch AI’s confidence range (161.8–169.4); the tick marks the median scored model.
Scores from Epoch AI, run independently of Anthropic.
The details
- Lab
- Anthropic
- Released
- Sep 28, 2026
- Knowledge cutoff
- Jun 2026
- Context window
- 1,000,000 tokens
- Max output
- 128,000 tokens
- Inputs
- Text, Images, PDFs
- Output
- Text
- Reasoning
- Adjustable effort low · medium · high · xhigh · max
- Tool calling
- Yes
- Structured output
- Yes
- Weights
- Proprietary
- API model ID
claude-sonnet-5-5on Anthropic- Availability
- 23 API providerslisted on models.dev
What Anthropic claims
Published by the lab at launch. Settings vary, so compare these only with care.
More from Anthropic
About Claude Sonnet 5.5
How much does Claude Sonnet 5.5 cost?
Claude Sonnet 5.5 costs $2.00 input / $10.00 output per million tokens (official Anthropic API price). Cached input is $0.20 per million tokens, and writing to the cache costs $2.50. At a 3:1 input-to-output mix that is $4.00 per million tokens, more expensive than 83% of the 360 priced models we track.
What is the context window of Claude Sonnet 5.5?
Claude Sonnet 5.5 accepts up to 1,000,000 tokens per request and can write up to 128,000 tokens in one response.
How good is Claude Sonnet 5.5?
Epoch AI gives Claude Sonnet 5.5 a Capabilities Index score of 165.2 (likely range 161.8–169.4), ranking it #3 of 148 models Epoch has scored. Epoch AI benchmark results: GPQA Diamond 95.6%, FrontierMath Tiers 1–3 88.8%, OTIS Mock AIME 2024–2025 100%, SimpleQA Verified 46.5%.
Is Claude Sonnet 5.5 open source?
No. Claude Sonnet 5.5 is proprietary; you use it through Anthropic’s API or partner platforms.
What inputs does Claude Sonnet 5.5 support?
Claude Sonnet 5.5 accepts text, images and PDFs and replies in text. It is a reasoning model with low, medium, high, xhigh and max effort settings, supports tool calling and can return structured JSON output.
When was Claude Sonnet 5.5 released?
Anthropic released Claude Sonnet 5.5 on Sep 28, 2026. Its training data runs to Jun 2026.
What are the best alternatives to Claude Sonnet 5.5?
The closest current models from other labs on capability, price and release date are GPT-6.1 Sol (OpenAI, $2.00 / $10.00), Grok 4.7 (xAI, $2.00 / $6.00), Kimi K3 (Moonshot AI, ECI 157.6, $3.00 / $15.00) and Qwen3.8 Max (Alibaba (Qwen), ECI 156.6, $2.00 / $6.00).