LLM engineering tools

Calculators and converters for building with LLMs: token cost, context windows, caching, VRAM, vector size, chunking, tool schemas, JSONL data and rate limits.

These tools help you plan and debug LLM applications before you spend money or GPU time. Prices and model limits come from the providers’ own pages, are shown with the date they were checked, and every calculation runs in your browser.

• LLM Token Cost Calculator

  Tokens in, cost per call, per 1,000 calls and per month.

• Context Window Checker

  Will your prompt, chunks and answer fit the context window?

• Prompt Caching Calculator

  Cached vs uncached input cost, and the break-even point.

• Local LLM VRAM Calculator

  Weights + KV cache + overhead, and whether it fits your GPU.

• Vector DB Size Calculator

  RAM and disk for N vectors at a given precision.

• RAG Text Chunker

  Split text by characters, tokens or sentences with overlap.

• Tool Schema Converter

  OpenAI ⇄ Anthropic ⇄ Gemini ⇄ MCP tool definitions.

• Fine-tuning JSONL Validator

  Line-by-line checks for chat-format training data.

• LLM Rate Limit Planner

  Max requests per minute, concurrency and queue time.

Looking for explanations? Read the guides, or see what changed recently in the changelog.