BLEU/ROUGE Calculator
Calculate BLEU and ROUGE scores for evaluating text generation
Text Pairs
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What are BLEU and ROUGE Scores?
BLEU (Bilingual Evaluation Understudy) and ROUGE (Recall-Oriented Understudy for Gisting Evaluation) are standard metrics for evaluating text generation quality. They compare generated text (candidate) against human-written text (reference) to measure similarity.
This calculator provides simplified implementations to help you understand these metrics and quickly evaluate LLM outputs against expected results.
Metric Comparison
BLEU Score
Precision-based: measures what fraction of candidate words appear in reference. Originally for machine translation.
ROUGE-L Score
LCS-based: finds longest common subsequence and computes F1. Good for summarization evaluation.
When to Use Each
| Metric | Best For | Limitation |
|---|---|---|
| BLEU | Translation, short outputs | Ignores recall |
| ROUGE-L | Summarization, articles | Order-sensitive only for LCS |
FAQ
Is this the full BLEU implementation?
This is simplified unigram BLEU. Full BLEU uses n-gram overlap (1-4) with brevity penalty. Use sacrebleu for research.
What's a good BLEU score?
It depends on the task. For translation, 40-60% is considered good. For paraphrasing, scores can be much lower even for quality output.