What Is a Token in ChatGPT & AI Models?
AI models like ChatGPT don't read word by word — they split text into tokens, which are chunks of characters. A token is roughly ¾ of a word in English, but the exact split depends on the model's tokenizer (BPE — Byte Pair Encoding).
2025–2026 Model Context Windows & Pricing
Token limits and API costs across all major models — updated June 2026.
| Model | Provider | Context Window | Input / 1M | Output / 1M |
|---|---|---|---|---|
| GPT-5.5 | OpenAI | 1.05M | $5.00 | $30.00 |
| GPT-5.4 | OpenAI | 1M | $2.50 | $15.00 |
| GPT-5.4 Mini | OpenAI | 1M | $0.40 | $1.60 |
| GPT-5.4 Nano | OpenAI | 1M | $0.20 | $1.25 |
| GPT-4.1 | OpenAI | 1M | $2.00 | $8.00 |
| Claude Opus 4.8 | Anthropic | 200K | $15.00 | $75.00 |
| Claude Sonnet 4.6 | Anthropic | 200K | $3.00 | $15.00 |
| Claude Haiku 4.5 | Anthropic | 200K | $0.80 | $4.00 |
| Gemini 2.5 Pro | 1M | $2.00 | $12.00 | |
| Gemini 2.5 Flash | 1M | $0.15 | $0.60 |
Frequently Asked Questions
How accurate is this token counter?
For OpenAI models (GPT-4, GPT-3.5, etc.) this tool uses a JavaScript implementation of BPE tokenisation based on the cl100k_base vocabulary — the same encoding OpenAI uses internally. Accuracy is within 1–3% for typical English text. For Claude and Gemini, tokens are estimated using their documented ratios and are within ~5% for English.
What happens when I exceed the context window?
When a conversation exceeds the model's context window (e.g. 128K for GPT-4), the model silently drops the oldest messages. This causes "forgetting" — the AI loses track of earlier context. You'll see a warning bar in this tool when you approach the limit.
Do tokens include spaces and punctuation?
Yes. Spaces, commas, periods, and special characters all consume tokens. In GPT tokenisation, a leading space is often merged with the following word into a single token (e.g. " cat" is one token). This is why raw character counts can mislead — use a token counter for accuracy.
How can I reduce my token count?
Key strategies: (1) Remove filler phrases like "Please note that…" or "As an AI…", (2) Use bullet points instead of prose for lists, (3) Shorten system prompts — they're sent with every request, (4) Avoid repeating context the model already has, (5) Use abbreviations where unambiguous, (6) Break large tasks into multiple shorter conversations.
Is my text stored or sent anywhere?
No. All tokenisation happens 100% in your browser using JavaScript. Your text never leaves your device and is never sent to any server. This tool has no backend and requires no login.
Why does code use more tokens than regular text?
Programming languages contain many special characters (brackets, semicolons, operators) and short identifiers that don't appear in BPE's vocabulary. These get split into multiple tokens. Indentation using spaces is especially costly — 4 spaces can equal 1–4 tokens.
More Free AI & Math Tools on Calcxi.com
GCF Calculator, LCM, Percentage, Fraction Simplifier, and 50+ more — all free, all with step-by-step explanations.
Browse All Tools →