Question 1

How do I count tokens before making an API call?

Accepted Answer

Use the tiktoken library (Python: pip install tiktoken). For GPT-4o: encoding = tiktoken.encoding_for_model('gpt-4o'); tokens = len(encoding.encode(text)). Alternatively, the OpenAI Tokenizer Playground at platform.openai.com/tokenizer shows exact token counts interactively.

Question 2

What is the context window and how does it affect cost?

Accepted Answer

The context window is the maximum total tokens (input + output) a model can process in one call. GPT-4o supports 128K tokens. Every token in your message history counts as input tokens — long conversations become expensive. Use context compression or summarisation for long-running agents.

Question 3

Does OpenAI offer cheaper batch pricing?

Accepted Answer

Yes. The Batch API offers 50% discount on all models for asynchronous requests that complete within 24 hours. Ideal for classification, summarisation, or embedding tasks that don't need real-time responses. The same endpoint costs $1.25/1M input tokens for GPT-4o instead of $2.50.

Question 4

How can I reduce my OpenAI API costs?

Accepted Answer

Key strategies: (1) Cache responses for identical inputs using a hash map or Redis. (2) Use GPT-4o mini for classification/extraction tasks. (3) Reduce system prompt length — it's charged on every call. (4) Use streaming to fail fast on bad outputs. (5) Batch API for offline processing. (6) Fine-tuning can produce a smaller model with similar quality at lower cost for specific tasks.

Question 5

What is the difference between tokens and words?

Accepted Answer

Tokens and words are not the same. In English, 1 token ≈ 0.75 words. Common words are often a single token; rare words and non-English text may use 2–4 tokens per word. 'Hello world' = 2 tokens; 'Electroencephalography' = 5 tokens; Chinese/Japanese characters use 2–3 tokens each.

Model	Input /1M	Output /1M	Best for
GPT-4o mini	$0.15	$0.60	High-volume, cost-sensitive apps
GPT-4o	$2.50	$10.00	Balanced quality & cost
o1-mini	$3.00	$12.00	Reasoning tasks, moderate cost
o1	$15.00	$60.00	Complex reasoning, research
GPT-4 Turbo	$10.00	$30.00	Legacy high-quality tasks

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