Prompt Length Checker
When working with large language models, understanding your prompt's length in tokens is critical — every model has a finite context window, and exceeding it means your input gets truncated or rejected entirely. This tool analyzes your prompt in real-time, showing token count, character count, and word count simultaneously. It displays visual progress bars for GPT-4's 128K window, Claude's 200K window, and Gemini's 1M window so you can see at a glance how much capacity you have left. Beyond raw counting, the tool offers AI-powered optimization suggestions that analyze your prompt's structure and recommend specific ways to reduce token usage while maintaining effectiveness. This is especially valuable when working with system prompts, long documents, or complex multi-step instructions that need to fit within model limits.
When should you use it?
- check_circle Checking whether a long system prompt fits within GPT-4's context window before deploying it in production
- check_circle Optimizing a complex multi-step instruction prompt to reduce API costs by minimizing token usage
- check_circle Verifying that a document plus prompt will fit within Claude's context window for summarization tasks
- check_circle Comparing prompt length across iterations to track optimization progress during prompt engineering
- check_circle Identifying which sections of a lengthy prompt consume the most tokens to prioritize compression efforts
How it works
The length analysis runs entirely in your browser as you type, providing instant feedback without any server round-trips. Token estimation uses the industry-standard approximation of roughly 4 characters per token for English text. While actual tokenization varies between models (GPT uses tiktoken, Claude uses its own tokenizer), this approximation is accurate within 10-15% for typical English prompts and gives you a reliable working estimate.
The context window visualization calculates what percentage of each model's maximum input your prompt occupies. This is displayed as color-coded progress bars — green when you are well within limits, yellow as you approach capacity, and red if you exceed the model's context window. The three models shown (GPT-4 at 128K, Claude at 200K, Gemini at 1M) represent the most popular AI platforms and their current maximum context sizes.
The AI optimization feature uses Gemini 2.0 Flash via streaming to analyze your prompt's structure and suggest specific improvements. These suggestions might include consolidating redundant instructions, replacing verbose phrases with concise alternatives, or restructuring sections to reduce token overhead while preserving your prompt's intent and effectiveness.
Frequently Asked Questions
Related tools
How to use
Paste your prompt to see token counts, model limits, and get AI-powered optimization tips.
Token estimate: ~4 chars per token.
- check_circle Real-time token & character counts
- check_circle GPT-4, Claude & Gemini limit bars
- check_circle AI-powered optimization suggestions