Calibration as a First-Class Criterion in LLM Evaluation

Mario Sanz-Guerrero, Katharina von der Wense


Abstract
Calibration of language models – the alignment between expressed or implicit confidence and empirical correctness – is a well-studied subfield within NLP. Methods to measure it already exist. The problem is adoption: outside this subfield, NLP research regularly introduces new models, datasets, and benchmarks without checking whether the model’s confidence scores are meaningful. We argue that this adoption gap is a major obstacle to trustworthy LLM evaluation. Miscalibration causes problems in two distinct areas: at deployment, where overconfident mistakes cause real harm, and inside the research pipeline, where methods like LLM-as-a-judge, synthetic data generation, and active learning rely on calibrated confidence without verifying it. Standard calibration metrics only require two inputs per example: a confidence score and a correctness judgment. Most benchmarks in use today already provide both, meaning calibration can be reported immediately. For open-ended generation, however, defining these two inputs is still an open challenge. We argue that each NLP subfield should pair its main performance metric with a calibration score and call for treating calibration as an essential property of every model rather than a niche topic.
Anthology ID:
2026.uncertainlp-main.6
Volume:
The Proceedings of the Third Workshop on Uncertainty-Aware NLP
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Wilker Aziz, Jonathan Berant, Bryan Eikema, Evgenia Ilia, Marie-Catherine de Marneffe, Barbara Plank, Artem Shelmanov, Swabha Swayamdipta, Jörg Tiedemann, Artem Vazhentsev, Raúl Vázquez, Chrysoula Zerva
Venues:
UncertaiNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
73–80
Language:
URL:
https://aclanthology.org/2026.uncertainlp-main.6/
DOI:
Bibkey:
Cite (ACL):
Mario Sanz-Guerrero and Katharina von der Wense. 2026. Calibration as a First-Class Criterion in LLM Evaluation. In The Proceedings of the Third Workshop on Uncertainty-Aware NLP, pages 73–80, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Calibration as a First-Class Criterion in LLM Evaluation (Sanz-Guerrero & von der Wense, UncertaiNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.uncertainlp-main.6.pdf