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Prompt Token Counter — Free Online Tool

Estimate token count and AI API cost for any prompt across GPT-4o, Claude, and Gemini. Live updates, 100% private.
Quick Answer

ZerofyTools Prompt Token Counter estimates the number of tokens in any AI prompt and shows the input cost across 6 major models — GPT-4o, GPT-4o mini, o3, Claude Sonnet, Claude Opus, and Gemini 2.5 Pro. Everything updates live as you type. No API calls, no uploads, 100% private.

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How do I use the Prompt Token Counter?

Estimate token count and AI API cost for any prompt across GPT-4o, Claude, and Gemini. Live updates, 100% private. This tool runs entirely in your browser — your files and data never leave your device. No registration, no watermarks, no limits.

01
Paste your system prompt, user message, or full conversation into the textarea.
02
Token count, character count, word count, and line count update instantly.
03
Click any model card to see the detailed cost breakdown for that model.
04
The context window progress bar turns amber at 60% usage and red at 90%.
05
Cost × 1,000 calls shows projected monthly API spend at scale.

What are the key features of the Prompt Token Counter?

  • ✓Live token estimation using a pure JS character-ratio algorithm — no external API calls.
  • ✓Cost breakdown across 6 models: GPT-4o, GPT-4o mini, o3, Claude Sonnet, Claude Opus, Gemini 2.5 Pro.
  • ✓Context window progress bar per model — turns amber at 60%, red at 90%.
  • ✓Detailed panel: remaining capacity, % used, single-call cost, and cost for 1,000 calls.
  • ✓100% private — your prompt text never leaves your browser.

Why use this tool and other frequently asked questions?

How accurate is the token estimate?
The estimator uses a character-ratio heuristic that approximates tiktoken and Anthropic's tokenizer within ~5–10% for typical English prompts. Non-Latin characters (CJK, Arabic, emoji) may be less accurate.
Are my prompts sent to any server?
No. All calculation happens locally in your browser using JavaScript. Your prompt text is never transmitted anywhere.
Why does cost × 1,000 calls matter?
Developers running prompts at scale need to budget monthly, not per-call. Multiplying by 1,000 gives a realistic cost estimate for production workloads.
Which prices are used?
Prices are public list prices (input tokens only) at the time of publication. Output tokens are billed separately. Always verify current pricing on the provider's pricing page before budgeting.

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Prompt Token Counter Free – Online Tool, No Signup | ZerofyTools