# What is a token in AI?

The small piece of text a language model reads and writes, often part of a word. Prices, limits and the context window are all counted in tokens.

- Page: https://tecyfy.com/concepts/token
- Subject: How AI works (https://tecyfy.com/concepts)
- Level: beginner
- The lesson: How AI writes its answers: one piece at a time (https://tecyfy.com/learn/how-ai-works/how-ai-writes)
- Last checked: 2026-10-14

A language model does not read letters or whole words. It reads tokens: short pieces of text that can be a single character, part of a word, a whole word or a punctuation mark. Common words are often 1 token each, and rarer words are split into several. Spaces count too, because they change where the text is cut.

As a rough guide for English, 1 token is about 4 characters, or three-quarters of a word, in OpenAI's counting. For Claude it is about 3.5 characters. The language changes the count too, and the same sentence gives different counts on different models, because each maker cuts text with its own [Tokenizer](https://tecyfy.com/concepts/tokenizer).

## Why it matters to you

Almost everything you pay for or run into is counted in tokens.

- **The bill.** API prices are per million input tokens and per million output tokens, and output costs more.
- **The limit.** The [context window](https://tecyfy.com/concepts/context-window), the most a model can see at once, is a number of tokens.
- **The speed.** A model writes 1 token at a time, each one predicted from everything before it. A longer answer takes longer.

## Not only text

Pictures and sound are turned into tokens as well. For Gemini, an image up to 384 pixels on each side counts as 258 tokens, and audio counts as 32 tokens for every second. A long recording can fill a window faster than you would guess.

## The tokens you never see

A model that thinks before it answers writes its reasoning in tokens too. You may not see them, but they are counted and billed as output, at the higher price. So 2 models with the same price per token can give very different bills for the same job: the one that thinks longer, or takes more steps, uses more tokens.

## How to count them

OpenAI publishes its tokenizer so you can count GPT tokens yourself, and the other makers' API documentation explains how to count theirs. When cost matters, count a real example rather than guess from the word count. And compare the cost of the whole job, not the price per token.

## Related

- [Tokenizer](https://tecyfy.com/concepts/tokenizer): The part that cuts text into the tokens a model reads, and turns the model's tokens back into text. Each model family has its own.
- [Context Window](https://tecyfy.com/concepts/context-window): Everything a model can see at once while it writes an answer, counted in tokens. When the window is full, something has to be left out.
- [Large Language Model](https://tecyfy.com/concepts/large-language-model): A model trained on a huge amount of text to predict the next token. Further training turns it into an assistant that follows instructions.

## Sources

- [Understanding and counting tokens](https://help.openai.com/en/articles/4936856-what-are-tokens-and-how-to-count-them), OpenAI Help Center, 2026-10-14. A token can be a character, part of a word, a whole word or punctuation, and spaces affect how text is divided. For English, 1 token is about 4 characters or three-quarters of a word. The same text can give different token counts depending on the model, its encoding and the language. Output tokens include, for reasoning models, reasoning tokens that are not shown as answer text.
- [Glossary](https://platform.claude.com/docs/en/about-claude/glossary), Anthropic, Claude API documentation, 2026-09-25. A language model generates text one token at a time, and a token is about 3.5 characters for Claude.
- [Understand and count tokens](https://ai.google.dev/gemini-api/docs/tokens), Google, Gemini API documentation, 2026-10-14. Pictures and sound are turned into tokens too. For Gemini, an image of up to 384 pixels on each side counts as 258 tokens and audio counts as 32 tokens a second.
- [Reasoning tokens](https://openrouter.ai/docs/use-cases/reasoning-tokens), OpenRouter documentation, 2026-10-14. Reasoning tokens are counted as output tokens and charged as output tokens.