What Is the OpenAI GPT Token Cost Calculator?
This calculator helps you estimate the cost of using OpenAI's GPT API based on the number of tokens you send and receive. OpenAI charges by tokens — small chunks of text — and prices differ for input (the prompt you send) and output (the model's response). Pricing is in US dollars (USD) and applies globally to anyone using the OpenAI API. Because token costs are easy to underestimate at scale, this tool gives you a quick projected price before you commit to a workload.
How to Use It
- Enter the number of input tokens (your prompt or request).
- Enter the number of output tokens (the model's expected reply).
- Select the GPT model you plan to use.
- Read the projected cost instantly.
As a rough rule of thumb, 1,000 tokens is about 750 words of English text. To convert words to tokens, multiply your word count by roughly \(1.33\).
The Formula Explained
The total cost is calculated by pricing input and output tokens separately, since output usually costs more:
$$\text{Total cost} = \left(\frac{\text{Input tokens}}{1{,}000{,}000}\times \text{Input price}\right) + \left(\frac{\text{Output tokens}}{1{,}000{,}000}\times \text{Output price}\right)$$
Most OpenAI models are priced per million tokens. The calculator divides your token counts by one million, multiplies by the per-model rate, and sums the two parts.
Worked Example
Suppose you send 500,000 input tokens and generate 200,000 output tokens with a model priced at $2.50 per million input tokens and $10.00 per million output tokens:
- Input: \(500{,}000 \div 1{,}000{,}000 \times \$2.50 = \$1.25\)
- Output: \(200{,}000 \div 1{,}000{,}000 \times \$10.00 = \$2.00\)
- Total: $3.25
Frequently Asked Questions
Why do output tokens cost more than input tokens? Generating text is more compute-intensive than reading it, so OpenAI typically charges a higher rate for output tokens.
How accurate is this estimate? It is a projection based on the rates you select. Actual bills depend on current OpenAI pricing and your real token usage, so always confirm rates on OpenAI's official pricing page.
Does this include extra costs? No. Features like fine-tuning, image generation, or cached input pricing may carry separate charges not reflected here.
