Understanding LLM Tokenization and API Pricing
Large Language Models do not process raw text strings directly. Instead, text is split into sub-word byte pair encodings (BPE) called tokens. A token can represent a single character, a sub-word root, or a whole word depending on the LLM's vocabulary size.
Frequently Asked Questions
What is an AI token?
A token is the basic unit of text processing used by Large Language Models (LLMs). In English, 1 token is approximately equal to 4 characters or 0.75 words. For example, 100 tokens equal roughly 75 words.
How many tokens are in a page of text?
A typical single-spaced page of text containing 500 words is equal to approximately 660 to 700 tokens.
What is context window capacity?
The context window is the maximum number of tokens an AI model can read and process in a single conversation prompt (e.g. 128k tokens for GPT-4o, 200k for Claude 3.5 Sonnet, and 2M tokens for Gemini 1.5/2.0).
Why do AI models bill separately for Input vs Output tokens?
Input tokens (prompt reading) require parallel GPU matrix multiplication, whereas Output tokens (completion generation) require sequential auto-regressive generation step by step, making output tokens 3x–4x more expensive to compute.
How does GPT-4o tokenization compare to Claude 3.5?
GPT-4o uses the o200k_base tokenizer which compresses code, non-English languages, and JSON structured data up to 20% more efficiently than older cl100k_base tokenizers.
Is my text data stored or sent to any server?
No. The AI Token Calculator runs 100% locally in your web browser. No prompt text is uploaded to any server or logged in any database.
What is prompt caching and how does it affect token cost?
Prompt caching allows developers to cache repeated system prompts or static documentation blocks, cutting input token costs by 50%–90% on Anthropic Claude and OpenAI APIs.
Is this token calculator free to use?
Yes. ToolzTotal provides 100% free online developer and AI tools with no signups, no subscriptions, and zero limits.
Sources & References
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