What this calculator does
This openai api cost calculator is built for the moment you need a defensible number — quoting a client, comparing options, or checking someone else's math — not a generic estimate.
This calculator estimates your OpenAI API bill. Choose a specific OpenAI model — GPT-4o, GPT-4o mini, GPT-4 Turbo, o1, o1-mini or GPT-3.5 Turbo — and see how tokens and traffic translate into monthly cost.
How to use the OpenAI API Cost Calculator
- Pick the model or enter its per-million-token prices.
- Enter average input & output tokens per request and monthly request volume.
- Review the monthly cost, per-request cost and input/output split chart.
The formula
monthly_cost = ((input_tokens × input_price + output_tokens × output_price) ÷ 1,000,000) × requests_per_month
Worked example
GPT-4o at 1,000 input + 500 output tokens across 5,000 requests: ((1,000 × $2.50 + 500 × $10.00) ÷ 1,000,000) × 5,000 = $37.50/month.
Common mistakes
- Confusing 1,000-token pricing with 1,000,000-token pricing — always check the unit.
- Only counting the user message and ignoring assistant/system tokens in the input.
- Assuming reasoning models cost the same as chat models — o1 output is 6× GPT-4o output.
When to use it
Use to compare OpenAI models before choosing one for production and to set a monthly budget alert.
Pro tips for the OpenAI API Cost Calculator
- The chart updates live — drag values up and down to build intuition for how the formula behaves.
- Change one input at a time to see which lever actually moves the answer the most.
- Round-trip check: reverse the inputs to confirm the formula matches what you'd compute by hand.
Frequently asked questions
›How is cost calculated?
Cost = (input tokens × input price + output tokens × output price) ÷ 1,000,000, then multiplied by monthly requests.
›What is a token?
Roughly 4 characters or ¾ of an English word. 1,000 tokens ≈ 750 words.
›Are prices real-time?
No — prices reflect published list rates and can change. Verify with the provider before budgeting.
›Does this include fine-tuning or images?
No. This estimator covers text chat/completion tokens only.
›How do I count tokens?
Use OpenAI's tiktoken library. As a rule of thumb, 1 token ≈ 4 characters of English.
›Do reasoning tokens count?
Yes — for o1/o3 the hidden reasoning tokens are billed as output tokens even though you don't see them.
›Where does the formula come from?
The formula shown in the "How it works" section is the same one you'll find in standard developer & utility references — no proprietary tweaks or hidden weightings.
›Does the OpenAI API Cost Calculator store the numbers I enter?
No. All math runs locally in your browser — nothing is sent to a server, and closing the tab discards the inputs unless you save them to favorites.
LLM pricing comparison
Prices per 1M tokens, USD| Provider | Model | Input | Output | Context |
|---|---|---|---|---|
| OpenAI | GPT-4o | $2.500 | $10.00 | 128k |
| OpenAI | GPT-4o mini | $0.150 | $0.60 | 128k |
| OpenAI | o1 | $15.000 | $60.00 | 200k |
| Anthropic | Claude 3.5 Sonnet | $3.000 | $15.00 | 200k |
| Anthropic | Claude 3.5 Haiku | $0.800 | $4.00 | 200k |
| Anthropic | Claude 3 Opus | $15.000 | $75.00 | 200k |
| Gemini 1.5 Pro | $1.250 | $5.00 | 2M | |
| Gemini 1.5 Flash | $0.075 | $0.30 | 1M | |
| Meta | Llama 3.1 405B (host) | $2.700 | $2.70 | 128k |
| DeepSeek | DeepSeek V3 | $0.270 | $1.10 | 64k |
Prices reflect public API list rates and may change — check each provider for current pricing before committing to spend.
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