How this Claude Token Calculator works
How Claude counts tokens
Claude uses Anthropic's own tokenizer, so the same text tokenizes to a different count than GPT — don't assume a GPT estimate transfers. Claude Opus 4.7 and later models use a newer tokenizer that Anthropic says produces about 30% more tokens for the same text: roughly 555,000 English words per 1M tokens (about 2.5 characters per token), against about 750,000 words on Claude Sonnet 4.6 and earlier. Anthropic's free token-counting endpoint gives exact figures for the model you name. The system prompt and prior conversation are resent on every turn, so input grows as a session lengthens.
Choosing the right Claude model
The verified lineup includes Claude Fable 5.1 at the highest standard token price, Claude Opus 5.5 and Opus 4.7 for demanding reasoning and agentic work, Claude Sonnet 5.5 as the balanced production default, and Claude Haiku 5.5 for fast, inexpensive, high-volume tasks. Claude Sonnet 4.6 and Haiku 4.5 remain available on the older tokenizer. Output is priced above input on each tier, so generation-heavy features lean on output cost — switch models in the calculator above to compare the same workload.
Prompt caching and what's excluded
Anthropic's distinctive lever is prompt caching: reusing a large, stable prefix such as a long system prompt or reference document sharply cuts the input cost of repeated calls. This calculator uses standard uncached pricing, so caching-heavy workloads cost less than shown. It also excludes the Batch API, tool use, and Claude Haiku 5.5's higher rates for prompts over 100,000 tokens (other current Claude models bill their full context window at standard rates) — verify the real numbers in the Anthropic console.