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AI subscription vs API cost calculator

Paying $20 a month for ChatGPT Plus, or thinking about the API instead? Set your usage below and see, for each model, whether the flat plan or the pay-per-token API is cheaper, and the point where it flips.

Prices last verified June 2026.

At 20 messages a day, the cheapest option is Grok via its API at about $1.58/mo.

  • Grok

    Grok 4.3

    API cheaper
    SuperGrok plan
    $30.00/mo
    API at usage
    $1.58/mo
    Break-even
    ~381 msgs/day

  • Gemini

    Gemini 3.1 Pro

    API cheaper
    AI Pro plan
    $19.99/mo
    API at usage
    $6.36/mo
    Break-even
    ~63 msgs/day

  • Claude

    Claude Opus 4.8

    API cheaper
    Pro plan
    $20.00/mo
    API at usage
    $13.50/mo
    Break-even
    ~30 msgs/day

  • ChatGPT

    GPT-5.5

    API cheaper
    Plus plan
    $20.00/mo
    API at usage
    $15.90/mo
    Break-even
    ~25 msgs/day

Estimates only. API cost = messages x 30 days x people x (input + output tokens at each model's rate). Token counts come from the length presets, so real bills vary with your actual prompts. The flat plans have usage limits of their own.

How this calculator works

A flat plan (like ChatGPT Plus) is a fixed monthly fee. The API charges for what you use, per token, where a token is roughly three quarters of a word. We estimate your monthly API cost as messages per day, times 30 days, times the number of people, times the cost of one message at each model's input and output token rates. The length preset sets how many tokens a message uses. The break-even column is the daily message volume where the API and the plan cost the same; below it the API is cheaper, above it the plan wins.

These are estimates, not a bill. Real costs move with your actual prompt lengths, and the flat plans carry their own usage limits. We compare the four assistants that have both a public flat plan and a public API price; DeepSeek (no flat plan, very cheap API) and Perplexity (it routes other models) are left out on purpose. For how the models actually differ in quality, see our best AI chatbot comparison.

Frequently asked questions

Is the API cheaper than a ChatGPT Plus subscription?

It depends on how much you use it. The API charges per token, so at light usage it costs far less than a $20 plan, but heavy daily use crosses a break-even point where the flat subscription wins. This calculator shows that break-even for each model at your message volume.

What counts as a 'message' here?

One message is a single back-and-forth: your prompt plus the model's reply. The length preset sets how many tokens each message uses, since longer prompts and answers cost more on the API.

Why isn't the API always cheaper?

API pricing scales with usage, so it only stays cheap while your volume is low. A flat plan is a fixed monthly fee no matter how much you chat, so above a certain daily volume the subscription becomes the better deal. The two lines cross at the break-even point.

Which is cheapest overall?

Grok and Gemini have the lowest API token prices, so they stay cheaper on the API for longer; ChatGPT and Claude cost more per token. But the right pick depends on your usage and which model you prefer, not price alone. See our best AI chatbot comparison for quality.

Sources

  1. ChatGPT (GPT-5.5) plan and API pricing: https://openai.com/api/pricing/
  2. Claude (Claude Opus 4.8) plan and API pricing: https://claude.com/pricing
  3. Gemini (Gemini 3.1 Pro) plan and API pricing: https://ai.google.dev/gemini-api/docs/pricing
  4. Grok (Grok 4.3) plan and API pricing: https://docs.x.ai/developers/models

Prices change often. We recheck and update them; this set was last verified in June 2026. Confirm the current rate on each official page before you commit.