What Is a Token in AI? A Simple Explanation

How Tokens Work

Before an AI model can read or write anything, it breaks text into small pieces called tokens. Think of it like how a spell-checker processes one word at a time — except tokenizers often split words into smaller chunks. The word "understanding" might become two tokens: "understand" and "ing."

This process is called tokenization. Every piece of text you send to an AI — your prompt, instructions, and any context — gets split into tokens before the model processes it. The model's response gets generated one token at a time, too.

Different AI models use different tokenizers, so the exact same text can produce slightly different token counts depending on the model. GPT, Claude, and Gemini each have their own tokenizer. However, the ratio of roughly 0.75 words per token (or 1.33 tokens per word) holds well across all of them for typical English text.

Numbers, code, and non-English text tend to use more tokens per word. A line of Python code averages about 10 tokens, and languages with longer words or non-Latin scripts can use 2–3× more tokens than English for the same meaning.

What Does 1 Million Tokens Look Like?

A million tokens is the standard billing unit for AI APIs. Here's what that actually looks like in terms you can picture:

Every estimate shows its assumption. See all 16 comparisons on the main page →

How Much Do Tokens Cost?

AI companies charge separately for input tokens(what you send) and output tokens (what the model writes back). Output always costs more — typically 3–6× more — because generating text requires far more computation than reading it.

Here's what a few popular models charge per million tokens:

ModelInput / 1M tokensOutput / 1M tokens
Claude Sonnet 5$2$10
GPT-5.5$5$30
Claude Haiku 4.5$1$5
Gemini 3 Flash$0.50$3

Prices range from $0.50 to $180 per million tokens — a huge spread. See all model prices →

Token Calculator

Want to estimate how much your specific use case will cost? Use our calculator to pick a model, set a budget, and see exactly how many words, pages, or lines of code that buys.

Open the token calculator →

Frequently Asked Questions

How many tokens is 1 word?
On average, one English word is about 1.33 tokens. This varies by word length and the specific tokenizer — short common words like "the" or "is" are usually one token, while longer or rarer words get split into multiple tokens.
How many tokens is 1 page?
A single-spaced page of text (about 500 words) is roughly 670 tokens. A double-spaced page (~250 words) is about 335 tokens.
Why do AI companies charge per token?
Tokens provide granular, usage-based billing. Instead of charging flat fees, per-token pricing means you only pay for what you actually use — whether that's a single sentence or an entire novel. It also reflects the real computational cost: processing more text requires more compute.
Are tokens the same across different AI models?
Similar, but not identical. Each model family (GPT, Claude, Gemini) uses its own tokenizer, so the same text can produce token counts that differ by up to 30%. However, the rule of thumb of 1 token ≈ 0.75 English words holds reasonably well across all major models.
What's the difference between input and output tokens?
Input tokens are what you send to the model — your prompt, instructions, and any context. Output tokens are what the model writes back — its response. Output tokens cost 3–6× more than input tokens because generating text is far more computationally expensive than reading it.