PromptItIn logoPromptItIn
Log in
Tokens & cost

Context window checker

Paste a document or open a text file. See how much of each model's context window it fills, and whether there's room left for the answer.

Free tool · Updated

0

Tokens (estimate)

0

Words

0

Characters

Leave room for the answer
The answer shares the same window as your text.

OpenAI

GPT-6 Astra · 1.05M windowFits · 0.4% used
GPT-6.1 Sol · 1.05M windowFits · 0.4% used
GPT-6.1 Terra · 1.05M windowFits · 0.4% used
GPT-6 Luna · 1.05M windowFits · 0.4% used

Anthropic

Claude Fable 5.2 · 1M windowFits · 0.4% used
Claude Opus 5.5 · 1M windowFits · 0.4% used
Claude Sonnet 5.5 · 1M windowFits · 0.4% used
Claude Haiku 5.5 · 1M windowFits · 0.4% used

Google

Gemini 4 Carbon · 1M windowFits · 0.4% used
Gemini 4 Argon · 1M windowFits · 0.4% used
Gemini 4 Hydrogen · 1M windowFits · 0.4% used
Gemini 3.8 Flash · 1.05M windowFits · 0.4% used
Gemini 3.1 Flash-Lite · 1.05M windowFits · 0.4% used

Token counts are estimates at about 4 characters per token. Chat apps like ChatGPT can accept less per message than the API window shown here.

How to use it

  1. Paste your text, or open a text file from your computer.
  2. Pick how much room to leave for the answer.
  3. Check each model. Green fits; red is too long and shows by how much.

Tips

  • The window holds your text and the answer together, so leave room for the reply.
  • Models can miss details buried in a very long prompt. Put your question at the end, after the document.
  • If a file is too long, split it by chapter or section and ask about one part at a time.
  • Cut repeated headers, footers and boilerplate before pasting. They use tokens and add nothing.

Frequently asked questions

What is a context window?

The most text a model can take in at once, counted in tokens. It includes your prompt, any documents, earlier messages and the answer.

How big are today's context windows?

The current models from OpenAI, Anthropic and Google all take about 1 million tokens through their APIs. That's roughly 750,000 words.

Why does ChatGPT say my text is too long when it fits here?

Chat apps can set lower limits per message than the API window. If that happens, split the text into parts.

Is my document uploaded?

No. Files are read in your browser and nothing leaves your device.

AI Token CounterPaste any text to estimate its tokens, words and characters, and see how much of a 1M-token context window it fills. Free, private, runs in your browser.AI API Cost CalculatorEstimate what your prompts cost on OpenAI, Anthropic and Google models, per call and per month, using each provider's current prices. Free.ChatGPT Character CounterCount characters, words, sentences and tokens in any prompt or AI answer as you type. Free, private and runs in your browser.

All free tools

Want a full prompt, not just keywords?

PromptItIn turns a rough idea into a clear prompt for ChatGPT, Claude, Gemini or any image model. Free to start.

Open the prompt generatorAdd to Chrome, free