Scaling Laws for Mixed Quantization

Zeyu Cao, Yao Lai, Boyang Gu, Cheng Zhang, Pedro Gimenes, Jianqiao Lu, Xitong Gao, Jianyi Cheng, Robert D. Mullins, Yiren Zhao


Abstract
Post-training quantization (PTQ) of large language models (LLMs) reduces memory usage and accelerates inference while maintaining accuracy. However, it remains unclear how to select a quantization scheme that achieves target accuracy across different model scales. We introduce two parameters to characterize this: the quantization ratio Qr (proportion of parameters quantized to low precision) and the block size Qb (number of parameters sharing a scaling factor). Based on extensive experiments across multiple LLM families and scales, we propose a unified scaling law that predicts quantization-induced loss degradation as a function of Qr, Qb, and model size. Our scaling law reveals two practical implications: (1) larger models tolerate higher Qr, making mixed-precision increasingly effective at scale; (2) small Qb, commonly used in mixed precision, becomes unnecessary for large models, simplifying hardware design without sacrificing accuracy. These findings provide a principled recipe for quantizing LLMs in practical deployment.
Anthology ID:
2026.emnlp-main.142
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
3265–3308
Language:
URL:
https://aclanthology.org/2026.emnlp-main.142/
DOI:
Bibkey:
Cite (ACL):
Zeyu Cao, Yao Lai, Boyang Gu, Cheng Zhang, Pedro Gimenes, Jianqiao Lu, Xitong Gao, Jianyi Cheng, Robert D. Mullins, and Yiren Zhao. 2026. Scaling Laws for Mixed Quantization. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 3265–3308, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Scaling Laws for Mixed Quantization (Cao et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.142.pdf