Completion Token Counter
Estimate the number of tokens an LLM completion or response will generate.
Inputs
Estimated Completion Tokens
200
Step by step
Completion tokens: words × tokens/word
150 × 1.33
= 200
How it works
Completion token estimation helps predict API costs and ensures the model has enough room within the context window for its response. English text averages about 1.33 tokens per word with BPE tokenizers.
Formula
Completion Tokens
tokens = expected_words × tokens_per_word
- tokens_per_word
- Average tokens per word (≈1.33 for English)
Frequently Asked Questions
Can I control how many tokens the model generates?
Yes — most APIs have a max_tokens parameter that caps completion length. Setting it prevents runaway generation and controls costs.
Are completion tokens more expensive than prompt tokens?
With many providers (OpenAI, Anthropic), completion tokens cost 2-4x more per token than input/prompt tokens.