How much does Claude Sonnet 5 cost?

List pricing is $3/million input tokens and $15/million output tokens, with an introductory discount of $2/$10 through 31st August. However, the new tokenizer produces approximately 30% more tokens than Sonnet 4.6 for the same input, effectively raising costs by 30%.

What is Claude Sonnet 5's context window size?

It has a 1 million token context window and 128,000 maximum output tokens.

How does the tokenizer efficiency differ by language?

The same input text produces 1.42× more tokens for English, 1.33× more for Spanish, 1.27× more for Python code, and approximately the same cost for Simplified Mandarin compared to Sonnet 4.6.

Large Language ModelsSimon Willison's WeblogJul 1, 2026Jul 1, 2026, 10:00 JST

Claude Sonnet 5 launches with 1M token window, but tokenizer inflates costs

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3 Key Points

What happened
Anthropic released Claude Sonnet 5, a new AI model with performance close to its more expensive Opus 4.8 variant. The model has a 1 million token context window and 128,000 maximum output tokens. However, the new tokenizer produces approximately 30% more tokens than Claude Sonnet 4.6 for the same input, effectively raising the price by 30% despite list pricing remaining at $3/million input and $15/million output (with an introductory discount to $2/$10 through 31st August).
Why it matters
Sonnet 5 offers high performance at lower list prices, but the tokenizer change means real-world costs are higher than they appear. The model is less capable at cyber tasks than Anthropic's more powerful Mythos 5, which allowed the company to release it without US government restrictions. For developers and businesses using Claude, the effective price increase may offset the appeal of lower headline rates.
What to watch
The tokenizer efficiency varies by language—English text costs 1.42× more per token than Sonnet 4.6, Spanish 1.33×, Python code 1.27×, and Simplified Mandarin roughly the same. Adaptive thinking is enabled by default, and the model uses the same tools and platform features as Claude Sonnet 4.6.

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FAQ

How much does Claude Sonnet 5 cost?: List pricing is $3/million input tokens and $15/million output tokens, with an introductory discount of $2/$10 through 31st August. However, the new tokenizer produces approximately 30% more tokens than Sonnet 4.6 for the same input, effectively raising costs by 30%.
What is Claude Sonnet 5's context window size?: It has a 1 million token context window and 128,000 maximum output tokens.
How does the tokenizer efficiency differ by language?: The same input text produces 1.42× more tokens for English, 1.33× more for Spanish, 1.27× more for Python code, and approximately the same cost for Simplified Mandarin compared to Sonnet 4.6.

Simon Willison's WeblogRead Original Article

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