AI Subscription vs API Pay-per-Use Calculator (which is cheaper for my usage?)

How it works

API cost per message = (input tokens × input price + output tokens × output price) ÷ 1,000,000, with prices in US$ per million tokens. Month = per message × messages per day × days. Prompt caching, web search, image or file tools and taxes are not included. A subscription also gives you the app, file uploads and extra features, but has usage limits; the API needs a key, billing set-up and an app or tool of your own.

⚠ Estimates for information only — not financial advice.

FAQ

How many tokens is one chat message?

It depends on the model’s tokenizer, and Korean text usually needs more tokens than the same message in English. The app resends earlier messages, so input tokens grow as a conversation gets longer — the text-to-tokens estimator can help.

Is the API cheaper for light users?

Often yes — a few short questions a day cost cents. Heavy users with long conversations usually come out ahead with a subscription.

Checked 11 Nov 2026. API prices: newcalc data file of official pricing pages (developers.openai.com/api/docs/pricing, platform.claude.com/docs/en/about-claude/pricing, ai.google.dev/gemini-api/docs/pricing), checked 10 Nov 2026. Subscription price: your plan’s pricing page.