Vendor-neutral · Pricing updated daily
The reference toolkit for LLM engineers.
Token counting, cost estimation and model comparison — computed in your browser, with no affiliation to any model provider. Nothing you paste is uploaded.
Covers OpenAI, Anthropic, Google, Meta, Mistral and Cohere
Tools
Token Counter
Count OpenAI tokens with the model-matched tokenizer and compare them with labelled Anthropic and Gemini estimates.
OpenLLM Cost Estimator
Project monthly API spend across models from your token volume and request count.
OpenModel Comparison
Context windows, max output and per-million pricing for current models, sortable and filterable.
OpenContext Window Visualizer
See how much of a model’s context window your prompt actually uses.
OpenPrompt Formatter
Turn a conversation into the exact request shape each provider’s API expects.
OpenJSON Schema Generator
Generate function-calling schemas for OpenAI, Anthropic and Gemini from one definition.
OpenSystem Prompt Library
A curated library of system prompts, searchable by category.
OpenWhy the numbers differ
llmtools runs OpenAI’s real tokenizer rather than a chars-divided-by-four rule of thumb, because the two disagree badly on anything that is not plain English. The same paragraph of Chinese can differ by nearly half between OpenAI’s two encodings alone. Neither Anthropic nor Google publishes a tokenizer that runs in a browser, so Claude and Gemini figures are marked as estimates rather than dressed up as a count.