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API or subscription? Break-even calculator for AI tools

A subscription is a flat monthly price; the API charges for every token. Enter how you actually use an assistant and see which is cheaper, and at what usage the answer flips.

Last checked
Plan billing
Includes conversation history and attached context resent with every message.
Long chats resend history; providers bill cached reads at a discount.

Result

API cost per month · Anthropic Claude Sonnet 5.5$8.05Anthropic API prices
Claude Pro per month$20.00Claude plan details
Break-even≈ 99 messages/day

At this usage the API is about $11.95 per month cheaper than Claude Pro.

API cost at other usage levels

API cost at other usage levels
Messages/dayAPI / monthvs plan
10$2.01API cheaper
20$4.03API cheaper
40 ←$8.05API cheaper
80$16.10API cheaper
160$32.21plan cheaper

Not included: cache storage / agent tool fees

The API estimate covers tokens only. Prompt-cache storage and agent tool-call fees (web search, URL fetch, sandbox) would be extra.

Assumptions (read before deciding)
  • A subscription is a flat price with usage limits that vendors describe qualitatively and change often. We do not convert plans into a number of messages.
  • Limits Claude Pro lists: More usage than Free.
  • API costs use standard pay-as-you-go rates (USD, excl. tax), 22 days of use per month. Taxes, free tiers, tool calls and image/file features are not included.
  • Subscriptions bundle apps, features and models the API does not, and the API offers control and automation subscriptions do not. Price is only one part of the decision.

How the break-even is calculated

We price one message at the API model’s standard rates: your average input tokens (including the conversation history that is resent with each message, partly at the cached rate) plus the reply’s output tokens. The break-even is the subscription price divided by that cost per message, spread over the days you use it.

Example: Claude Pro costs $20.00 a month. With 40 messages a day on 22 days, 3,000 input tokens (half cached) and 600 output tokens per message, the same usage on the Anthropic Claude Sonnet 5.5 API costs about $8.05. The plan pays off above roughly 99 messages a day.

Why there is no “messages included” number

Vendors describe subscription limits qualitatively (“5x Pro usage”, “higher limits”) and adjust them often, so we show the limits they publish and let you set the usage. A heavy user who hits a plan’s limit is a strong signal that the API (or a bigger plan) is the better fit, whatever the price says.

Beyond price

Subscriptions include apps, file uploads, image generation and agent features with no extra metering. The API gives you automation, model choice and per-token control, but you pay for every retry and every long conversation.

For a product or team workload, use the LLM API workload cost calculator. To compare team plans by seat count, see the AI subscription cost calculator. All API rates are listed in the LLM API pricing table.