OpenAI Token Counter & API Cost Calculator (GPT-4o, GPT-4o mini & o3-mini)
Count OpenAI o200k_base BPE tokens and calculate Input, 50% Cached Input, and Output API costs for GPT-4o, GPT-4o mini, and o3-mini.
How do I use OpenAI Token Counter & API Cost Calculator (GPT-4o, GPT-4o mini & o3-mini)?
Notice the tool is pre-filtered to 'OpenAI (o200k_base)' with a sample OpenAI Structured Outputs (`response_format: json_object`) prompt and 50% Prompt Cache hit ratio.
Paste your OpenAI system prompt, `messages` JSON array, or function-calling tool definitions into the editor.
Adjust the 'Prompt Cache Hit Ratio' (0%, 50%, 75%, 90%) in the left sidebar to model automatic OpenAI Prompt Caching savings on prefixes ≥1,024 tokens.
Compare exact Input, Cached Input, and Output API costs across GPT-4o, GPT-4o mini, and o3-mini.
What features does OpenAI Token Counter & API Cost Calculator (GPT-4o, GPT-4o mini & o3-mini) offer?
Pre-filtered to OpenAI's flagship models: `GPT-4o`, `GPT-4o mini`, and `o3-mini Reasoning`
Models OpenAI's automatic 50% Cached Input discount on static system prompt prefixes (≥1,024 tokens)
Pre-loaded with an OpenAI Chat Completions JSON schema prompt for realistic token testing
Displays `o200k_base` tokenizer encoding badges and 128K / 200K context window saturation bars
1-Click switch to Anthropic Claude or Google Gemini to benchmark cross-provider migration savings
100% Client-Side privacy: proprietary system prompts and customer context never leave your browser
OpenAI `o200k_base` Tokenizer & 2026 API Pricing Reference
GPT-4o, GPT-4o mini, and o3-mini use OpenAI's 200,000-token `o200k_base` BPE vocabulary, which compresses code, JSON, and non-English text up to 25% more efficiently than legacy `cl100k_base`.
Cost = (UncachedTokens ÷ 1,000 × InputRate) + (CachedTokens ÷ 1,000 × 0.50 × InputRate)OpenAI automatically applies a 50% discount on cached input tokens for prompts ≥ 1,024 tokens in 128-token increments.
| OpenAI Model | Tokenizer Encoding | Input / 1M Tokens | Cached Input / 1M | Output / 1M Tokens | Context Window |
|---|---|---|---|---|---|
| GPT-4o | o200k_base | $2.50 | $1.25 (50% off) | $10.00 | 128,000 tokens |
| GPT-4o mini | o200k_base | $0.15 | $0.075 (50% off) | $0.60 | 128,000 tokens |
| o3-mini (Reasoning) | o200k_base | $1.10 | $0.55 (50% off) | $4.40 | 200,000 tokens |
How is OpenAI Token Counter & API Cost Calculator (GPT-4o, GPT-4o mini & o3-mini) used in real-world workflows?
Structuring System Prompts to Trigger OpenAI's ≥1,024 Token Cache Threshold
Place static instructions, few-shot examples, and tool schemas at the very beginning of your `messages` array (>1,024 tokens) to cut GPT-4o input costs by 50%.
Benchmarking GPT-4o vs. GPT-4o mini & o3-mini Unit Economics
See side-by-side how routing classification tasks from GPT-4o ($2.50/1M) to GPT-4o mini ($0.15/1M) reduces input token spend by 94%.
Auditing Function Calling & JSON Schema Token Overhead
Every tool definition in `tools: [...]` is billed as input tokens on every turn—paste your JSON schema here to measure its exact token footprint.
Frequently Asked Questions about OpenAI Token Counter & API Cost Calculator (GPT-4o, GPT-4o mini & o3-mini)
What is the difference between `o200k_base` and `cl100k_base` in OpenAI?
`cl100k_base` (100K vocabulary) was used by GPT-4 Turbo and GPT-3.5. `o200k_base` (200K vocabulary) is used by GPT-4o, GPT-4o mini, o1, and o3-mini, achieving fewer tokens per paragraph—especially for source code, JSON keys, and multilingual text.
How does OpenAI Prompt Caching work and how much does it save?
OpenAI automatically caches the longest matching prefix of prompts that are at least 1,024 tokens long. Cached input tokens receive a 50% price discount ($1.25/1M instead of $2.50/1M on GPT-4o) with zero code changes required.
Do reasoning tokens in `o3-mini` count as input or output tokens?
Internal chain-of-thought reasoning tokens generated by `o3-mini` and `o1` are billed at the model's **Output** token rate ($4.40 per 1M tokens on `o3-mini`) and count toward `max_completion_tokens`.
Are my prompts sent to the OpenAI API to count tokens?
No. Token estimation and pricing calculations run 100% locally in your browser.
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