How are AI API costs calculated?

AI APIs typically charge per token — a token is approximately 0.75 words or 4 characters. Costs are usually split between input tokens (your prompt) and output tokens (the AI's response). Prices vary significantly between models.

What is the difference between input and output tokens?

Input tokens are the text you send to the API (your prompt and context). Output tokens are the text the model generates in response. Output tokens typically cost 2–5x more than input tokens.

How can I reduce AI API costs?

To reduce costs: use smaller models when possible, implement prompt caching, keep prompts concise, batch requests efficiently, use streaming to detect early stops, and set max_tokens to limit response length for simple queries.

AI API Cost Calculator

Estimate monthly costs for using AI APIs like OpenAI and Anthropic. Enter your expected usage and model to calculate the monthly API bill.

Select AI model

Usage volume

API requests per day: 100

1 (personal)1,000 (small app)10,000 (large app)

Input tokens/request: 1 000

~750 words

Output tokens/request: 500

~375 words

Token estimates: Short question ≈ 50 tokens · Long prompt ≈ 500–2000 · Full document ≈ 5,000–20,000 · Short answer ≈ 100–300 · Long explanation ≈ 500–1,500

🟢 GPT-4o — OpenAI

0.690 cents

Cost/request

20.70 €

Month (30 days)

248.40 €

Year

Pricing: In $2.5/1M · Out $10/1M token · USD→EUR @0.92

Model comparison with same settings

Model	Cost/mo	Cost/yr	vs. selected
🟠 Gemini 1.5 Flash(Google)	0.62 €	7.45 €	97 % cheaper
🟡 GPT-4o mini(OpenAI)	1.24 €	14.90 €	94 % cheaper
🔵 Claude 3 Haiku(Anthropic)	2.42 €	28.98 €	88 % cheaper
🟢 GPT-4o(OpenAI)	20.70 €	248.40 €	← selected
🔴 Gemini 1.5 Pro(Google)	24.15 €	289.80 €	17 % more expensive
🟣 Claude 3.5 Sonnet(Anthropic)	28.98 €	347.76 €	40 % more expensive
⚫ GPT-4 Turbo(OpenAI)	69.00 €	828.00 €	233 % more expensive
🟤 Claude 3 Opus(Anthropic)	144.90 €	1738.80 €	600 % more expensive

Note: Prices are estimates from May 2026 and may change. Always check the latest pricing on the provider's website. All prices converted to euros at a rate of 0.92.

Token count: 1,000 tokens ≈ 750 English words / ~600 Finnish words.

The AI API cost calculator compares the prices of different language models and estimates how much your API usage will cost. Enter your usage volume to see a cost estimate and compare models such as GPT-4o, Claude and Gemini side by side.

How the calculator works and what it’s for▾

How the cost is formed

Language model pricing is typically based on processed tokens, meaning the amount of text in the input and the response. Different models charge a different price per thousand or million tokens, and input and output often carry different rates.

The calculator multiplies your usage by the model's price and shows an estimated total cost, letting you compare options with the same usage profile.

What you enter and what you get

You provide an estimated usage volume, such as tokens or number of requests, and choose the models to compare. In return you get a cost estimate for each model.

This lets you quickly see which option is cheapest for your particular needs.

Who it is for

The tool serves developers, product teams and entrepreneurs building AI applications who want to budget API costs in advance.

It helps choose a model that sensibly balances price against requirements.

Good to know

Prices and models change frequently, so check current pricing on the provider's pages. The calculator's result is an estimate based on the numbers you enter.

Real cost is also affected by request length, the model version and any additional features.

🔄 Reviewed June 2026