Understanding Tokens in LLMs
When working with Large Language Models (LLMs) like GPT-4, Claude, and others, understanding how text is processed as "tokens" is essential for both technical implementation and cost management.
What Are Tokens?
Tokens are the fundamental units that AI models use to process text. They're not exactly words or characters, but rather pieces of text that the model recognizes as single units. Depending on the model and tokenization algorithm, tokens can represent:
- Single characters (especially for uncommon ones)
- Parts of words (like common prefixes or suffixes)
- Complete words (for common, short words)
- Whitespace and punctuation
For example, the sentence "I love tokenization!" might be broken down into tokens like ["I", " love", " token", "ization", "!"].
The Mathematics of Tokens
At their core, tokens are numerical representations of text. The process works like this:
- Tokenization: The text is split into tokens according to the model's vocabulary
- Encoding: Each token is converted to a unique integer ID (typically ranging from 0 to 50,000+)
- Embedding: These integers are then converted to vectors (typically 768 to 4096 dimensions)
For instance, in many systems:
- "Hello" → token ID 11 → [0.1, -0.2, 0.5, ..., 0.3]
- "world" → token ID 233 → [-0.3, 0.1, 0.7, ..., -0.1]
Token Count Variability
Different languages and types of content tokenize differently:
- English text: Averages ~1.3 tokens per word
- Code: Often more token-efficient (many programming keywords are single tokens)
- Non-Latin scripts: Often less efficient (potentially 2-3x more tokens than English)
- Numbers: Digits are often separate tokens (making "123456" use 6 tokens)
- Whitespace: Usually counted as part of tokens
Token Economics
Understanding token counts directly impacts costs when using commercial LLM APIs:
-
Input vs. Output Costs:
- Most providers charge differently for input tokens (what you send to the model) versus output tokens (what the model generates)
- Output tokens are typically 2-5x more expensive than input tokens
-
Cost Calculation Example: If you're using GPT-4o which costs $2.50 per million input tokens and $10.00 per million output tokens:
- A 10,000 token conversation history (input) costs: 10,000 × ($2.50/1,000,000) = $0.025
- A 1,000 token response (output) costs: 1,000 × ($10.00/1,000,000) = $0.01
- Total cost: $0.035
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Context Window Considerations:
- Models with larger context windows (like Claude 3.7 Sonnet with 200K tokens) allow more text but can increase costs
- The entire context window counts as input tokens, even if you're only referencing a small portion
Token Optimization Strategies
To manage costs and improve performance:
-
Prompt Engineering:
- Be concise and specific in instructions
- Remove unnecessary boilerplate text and repetitions
-
Context Pruning:
- For chat applications, consider removing or summarizing older messages
- For document processing, extract only the most relevant sections
-
Chunking Strategies:
- For large documents, develop smart chunking strategies that preserve context while minimizing token usage
- Consider semantic chunking rather than arbitrary divisions
-
Model Selection:
- Use smaller, cheaper models for simpler tasks
- Reserve premium models for complex reasoning or generation
-
Token Counting Tools:
- Most providers offer tokenization libraries to estimate costs before API calls
- Examples: tiktoken (OpenAI), anthropic-tokenizer (Anthropic)
Real-world Token Counts
To provide perspective, here are approximate token counts for common items:
- One page of single-spaced text: ~500 tokens
- A 5-page document: ~2,500 tokens
- A short novel (50,000 words): ~65,000 tokens
- The entire works of Shakespeare: ~900,000 tokens
Understanding these token dynamics helps developers and businesses make informed decisions about LLM implementation, balancing capability needs with cost considerations.
Why Tokens Matter
Understanding tokenization is important for several reasons:
- Cost calculation: Most AI providers charge based on the number of tokens processed
- Context windows: Models have limits on how many tokens they can process in one request
- Prompt engineering: Crafting efficient prompts that use fewer tokens can reduce costs
- Performance optimization: Understanding token usage helps optimize applications
How Different Models Tokenize Text
Different LLM providers use slightly different tokenization algorithms:
Model Provider | Tokenizer | Typical Characters Per Token | Notes |
---|---|---|---|
OpenAI (GPT models) | tiktoken (BPE) | ~4 characters | Used for GPT-3.5, GPT-4, etc. |
Anthropic (Claude) | proprietary BPE | ~3.5-4 characters | Similar to tiktoken but with differences |
Google (Gemini) | SentencePiece | ~4-5 characters | Used for Gemini models |
Meta (Llama) | SentencePiece | ~4 characters | Used for Llama family of models |
LLM Pricing Details
Each AI provider has its own pricing structure based on tokens. Here's a breakdown of major LLM providers and their pricing models:
OpenAI Models
OpenAI offers several models with different capabilities and price points:
- GPT-4o: $2.50 per 1M input tokens, $10.00 per 1M output tokens
- GPT-4o Mini: $0.15 per 1M input tokens, $0.60 per 1M output tokens
- GPT-4.5-preview: $75.00 per 1M input tokens, $150.00 per 1M output tokens
- o1-preview: $15.00 per 1M input tokens, $60.00 per 1M output tokens
- o1-mini: $1.10 per 1M input tokens, $4.40 per 1M output tokens
- o1: $15.00 per 1M input tokens, $60.00 per 1M output tokens
- o3-mini: $1.10 per 1M input tokens, $4.40 per 1M output tokens
- GPT-4: $30.00 per 1M input tokens, $60.00 per 1M output tokens
- GPT-4-Turbo: $10.00 per 1M input tokens, $30.00 per 1M output tokens
- GPT-3.5-Turbo: $0.50 per 1M input tokens, $1.50 per 1M output tokens
Anthropic Models
Anthropic's Claude models are priced competitively with varying capabilities:
- Claude 3.7 Sonnet: $3.00 per 1M input tokens, $15.00 per 1M output tokens
- Claude 3.5 Sonnet: $3.00 per 1M input tokens, $15.00 per 1M output tokens
- Claude 3.5 Haiku: $0.80 per 1M input tokens, $4.00 per 1M output tokens
Google Models
Google offers several Gemini models at different price points:
- Gemini 2.0 Flash: $0.10 per 1M input tokens, $0.40 per 1M output tokens
- Gemini 2.0 Flash-Lite: $0.075 per 1M input tokens, $0.30 per 1M output tokens
- Gemini 1.5 Pro (128K context): $1.25 per 1M input tokens, $5.00 per 1M output tokens
- Gemini 1.5 Pro (2M context): $2.50 per 1M input tokens, $10.00 per 1M output tokens
- Gemini 1.5 Flash: $0.075 per 1M input tokens, $0.30 per 1M output tokens
Meta Models (via providers)
Meta's Llama models available through various hosting providers:
- Llama 3.3 70B: $0.23 per 1M input tokens, $0.40 per 1M output tokens
- Llama 3.1 405B: $1.79 per 1M input tokens, $1.79 per 1M output tokens
- Llama 3.1 70B: $0.23 per 1M input tokens, $0.40 per 1M output tokens
Other LLM Providers
Several other providers offer competitive alternatives:
- DeepSeek V3: $0.14 per 1M input tokens, $0.28 per 1M output tokens
- DeepSeek R1: $0.55 per 1M input tokens, $2.19 per 1M output tokens
- Mistral Large 2: $2.00 per 1M input tokens, $6.00 per 1M output tokens
- Mistral Small 24.09: $0.20 per 1M input tokens, $0.60 per 1M output tokens
- Mistral NeMo: $0.15 per 1M input tokens, $0.15 per 1M output tokens
- Amazon Nova Pro: $0.80 per 1M input tokens, $3.20 per 1M output tokens
- Cohere Command R: $0.50 per 1M input tokens, $1.50 per 1M output tokens
- Cohere Command R+: $3.00 per 1M input tokens, $15.00 per 1M output tokens
Token Optimization Strategies
Optimizing your prompts for token efficiency can significantly reduce costs, especially at scale. Here are some effective strategies:
Prompt Engineering Tips
- Be concise: Remove unnecessary words, examples, and redundant context
- Use efficient formatting: Some formatting approaches use fewer tokens than others
- Leverage system prompts: Put stable instructions in system prompts where supported
- Batch similar requests: Combine multiple similar questions into one prompt when possible
- Use JSON mode: For structured data, JSON mode can be more token-efficient
- Choose the right model: Smaller models often need more detailed prompts but cost less per token
Common Token Calculator Use Cases
Our token calculator is especially useful for:
- Prompt engineers: Optimize prompts for maximum efficiency
- AI application developers: Estimate costs before deployment
- Enterprise AI users: Budget for large-scale AI implementations
- Content creators: Understand token usage for batch processing of documents
- Researchers: Compare token efficiency across different prompt strategies
About Tokenizer Accuracy
This tool uses OpenAI's tokenization. While this provides a very good estimate for most models, there may be slight variations between different AI providers. For the most accurate counts, consider using provider-specific tokenizers when available.
People always ask
How much do tokens cost?
Token costs vary by model and whether they're input or output tokens. Input tokens (what you send to the model) typically cost 1/3 to 1/5 as much as output tokens (what the model generates). Prices range from $0.15 to $15.00 per million input tokens and $0.60 to $75.00 per million output tokens, depending on the model.
How many tokens is an average word?
In English, a word is typically about 1.3 tokens on average. However, this varies significantly:
- Common short words ("the", "a", "and") are often a single token
- Medium-length words may be 1-2 tokens
- Longer or uncommon words might be 3 or more tokens
- Technical terms, code, and non-English text often use more tokens per word
What is a context window?
The context window is the maximum number of tokens a model can process in a single request, including both input and output. Models like GPT-4o support up to 128,000 tokens in context, while others may support fewer. When planning applications, it's important to ensure your use case fits within the model's context window.
Do tokens affect temperature or other parameters?
No, tokens are only related to the text content processed by the model. Parameters like temperature, top_p, and frequency penalty control how the model generates text but don't affect token counts or costs.