ChatGPT API Cost Calculator

How API Token Pricing Actually Works

When calculating OpenAI API costs or Anthropic Claude API costs, developers often underestimate the ratio of Input to Output tokens. Large Language Models (LLMs) charge significantly different rates depending on whether they are reading text (Input) or generating text (Output).

The Input vs. Output Trap

For example, GPT-4o charges $5.00 per 1 Million input tokens, but $15.00 per 1 Million output tokens. This means an AI wrapper generating long-form content will burn through cash 3x faster than an app that just analyzes user text.

Tokens vs. Words

A common mistake in AI startup financial modeling is equating tokens to words. A standard rule of thumb is that 1 token equals roughly ¾ of an English word. Therefore, a 1,000-word essay requires approximately 1,333 tokens.

The AI Startup Burn Rate Trap

Unlike traditional SaaS where AWS infrastructure costs are largely fixed, Generative AI introduces variable costs on every single user interaction. If your pricing model does not account for heavy “power users”, a single user can cost you more in API fees than their monthly subscription revenue. This is why using a dedicated API Cost Calculator and translating those metrics directly into your SaaS Runway is critical for “Default Alive” survivability.