ChatGPT API vs ChatGPT Plus: which costs less?

ChatGPT Plus is a flat monthly subscription. The OpenAI API charges per use: you pay for the tokens you send and receive. For many people who mostly ask questions and get help with code, the API works out much cheaper. For heavy users of the chat app’s extra features, Plus can be better value.

Note

Prices below are examples at the time of writing. Always check openai.com/chatgpt/pricing and openai.com/api/pricing for current numbers.

How API pricing works

API prices are per million tokens, with separate input and output prices. A token is roughly ¾ of a word, so a 500-word answer is about 650 tokens.

cost = input tokens × input price + output tokens × output price

Example prices per 1M tokens:

Model	Input	Output
gpt-4o-mini	$0.15	$0.60
gpt-4o	$2.50	$10.00

Worked example

Say you send 50 messages a day, each with about 500 tokens in (your question plus some earlier conversation) and 500 tokens out. That’s 1,500 messages a month.

Model	Cost per message	Per month
gpt-4o-mini	500 × $0.15/1M + 500 × $0.60/1M ≈ $0.0004	≈ $0.56
gpt-4o	500 × $2.50/1M + 500 × $10/1M ≈ $0.0063	≈ $9.40

ChatGPT Plus costs $20 a month in the US (prices vary by country).

Two things push the API cost up:

• Long conversations. Every message re-sends the whole chat so far as input. Start a new chat when you change topic.
• Big inputs. Pasting whole files or logs adds input tokens.

When Plus is the better deal

• You use features that only exist in the ChatGPT app (image generation, voice, custom GPTs, file analysis in the browser).
• You send very long conversations all day with the largest models.
• You want a fixed bill and never think about tokens.

When the API is the better deal

• You mostly ask questions, write and debug code, or summarize text.
• You want to use other providers too (Claude, Gemini, Llama via Groq) without a subscription for each.
• You use AI in scripts and the terminal.

Measure instead of guessing

kunji is a free terminal app that shows the cost of every answer and keeps a local usage log:

pip install kunji
kunji keys add openai
kunji chat -m openai:gpt-4o-mini

After a week, check your real number:

kunji usage -d 7

Set a daily limit so there are no surprises:

kunji budget set openai 1

Costs can also be shown in rupees or any currency: see Costs and budgets.