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LLM API Cost Calculator

Paste a prompt and an expected output length to estimate the API cost across Claude, GPT, and Gemini models side by side. Prices are refreshed from a public model-pricing catalog every time the site is rebuilt.

Everything runs locally in your browser — your text is never sent to any server, only the price list is fetched ahead of time at build.

Guide: How to use & features

  • Paste a prompt or document into the text area and each model's input token count updates automatically.
  • "Expected output tokens" is a single number applied to every model, since there is no generated text to tokenize per model.
  • The table automatically sorts by total cost, cheapest first, and marks the cheapest model with a badge.
  • The $/1M column shows the per-million-token input and output price for each model, useful when choosing a model.

FAQ: FAQ

  • How up to date is the pricing data?

    It is refreshed automatically from a public model-pricing catalog (OpenRouter) every time this site is rebuilt. The page shows the "pricing data fetched" date so you can see exactly how fresh it is. If a refresh fails, the previously committed price is kept, so a price is never blank.

  • Does this match the official API pricing exactly?

    No, treat it as a reference. It relies on a third-party aggregator (OpenRouter) that publishes per-model prices, which can differ from a vendor's own announcement in timing or detail (batch discounts, prompt caching rates, long-context surcharges, etc.). Always check the vendor's official pricing page before making a purchasing or billing decision.

  • Why can't output tokens be counted from real text?

    The output hasn't been generated yet, so there is nothing to tokenize. Instead you enter an "expected output tokens" number, and that single value is applied to every model in the comparison. Adjust it up or down if you expect a shorter or longer response.

  • Why are the Claude and Gemini input token counts approximate?

    Same reason as the LLM Token Counter tool: Anthropic and Google do not publish their tokenizers, so those counts are estimated from the exact GPT count and the character mix, and can deviate from the real API count by roughly ±10–20%.

  • Is my prompt sent anywhere?

    No. Prompt analysis and cost calculation run entirely in your browser. The only network request involved is the price-list fetch, which happens once at build time — not while you are using the tool.

Use cases: Common use cases

  • Comparing model costs before choosing one

    See how the same prompt costs across Claude, GPT, and Gemini models side by side, and pick the one that fits your budget and requirements.

  • Estimating system-prompt costs

    Get a rough monthly cost estimate for a long system prompt or the context inserted by a RAG pipeline.

  • Understanding the cost gap between flagship and lightweight models

    See the concrete dollar difference between a flagship model (like an Opus-tier model) and a lightweight one (like a Haiku-tier model) for the same input/output volume.

  • Drafting a cost estimate for stakeholders

    Use it as a quick starting point when putting together a cost projection for adding an AI feature to a product.

Notes: Notes & limitations

  • Do not use this for billing

    The prices shown are reference values from a third-party aggregator and may differ from your actual invoice. Always check the vendor's official pricing page before making a formal estimate or purchasing decision.

  • The output token count is a hypothetical value

    The output cost is calculated from the "expected output tokens" you enter, applied equally to every model — not from an actual generated response. If real output length varies by model, the true cost gap may be larger or smaller than this estimate.

  • Cache discounts and long-context surcharges are not included

    Conditional pricing such as prompt-cache discounts, batch-API discounts, or surcharges above a 200K-token threshold are not applied. This is a simple input-price × input-tokens + output-price × output-tokens estimate.

  • Pricing only refreshes when the site is rebuilt

    The price data updates only when this site is rebuilt and redeployed. Right after a vendor changes their pricing, the "pricing data fetched" date shown on the page may lag behind.
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Applied to every model equally — there is no generated text to tokenize per model, so this is a single estimate you control.

Cost by model

Model Input tokens Output tokens $ / 1M in · out Est. cost
Claude Opus 4.8 0 0 $5 · $25 $0.00
Claude Sonnet 4.5 0 0 $3 · $15 $0.00
Claude Haiku 4.5 0 0 $1 · $5 $0.00
GPT-5.5 0 0 $5 · $30 $0.00
GPT-5 0 0 $1.25 · $10 $0.00
GPT-4.1 0 0 $2 · $8 $0.00
GPT-4o 0 0 $2.5 · $10 $0.00
GPT-4 Turbo 0 0 $10 · $30 $0.00
GPT-3.5 Turbo 0 0 $0.5 · $1.5 $0.00
Gemini 3 Pro 0 0 $2 · $12 $0.00
Gemini 2.5 Flash 0 0 $0.3 · $2.5 $0.00

Pricing data fetched: 2026-08-03 · Source: OpenRouter public model catalog (reference pricing, not official vendor pricing).

Costs are estimates for rough comparison only — not for billing. Claude and Gemini token counts are heuristic estimates (±10–20%), and per-model chat-API overhead (message structure, system prompt, tool definitions) is not included. Always check the vendor's own pricing page before making a purchasing decision.

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