← Blogby Marcell Almeida

How to check AI context window usage

Paste a prompt — see token estimate, context limit, usage percentage, and remaining capacity.

Every LLM has a context window limit. Exceed it and your request fails or gets truncated. The AI Context Window Calculator shows how much of GPT-4o, Claude, or Gemini capacity your text consumes.

Try it — pick a model and paste your text

Open full tool →

How it works

  1. Select a model — context limits differ (8K to 1M tokens).
  2. Paste your text — prompt, document, or code.
  3. Check usage bar — stay under 80% for safety margin.

Token estimation

Uses ~4 characters per token for English — same heuristic as the AI Token Counter. Close enough for planning; verify with the provider tokenizer for billing.

Cost planning

Once you know token count, plug into the AI Cost Calculator for per-request pricing.

The How to check AI context window usage is free, runs locally, and never sends your data to a server. More developer tools at maratool.com.