# Accuracy Metrics: RMSE, MAE, Precision@K, Recall@K, MAP, MRR, NDCG, HR@K — Full Math + NumPy

> Source: https://sukruyusufkaya.com/en/learn/oneri-sistemleri/dogruluk-metrikleri-rmse-ndcg-map-numpy
> Updated: 2026-05-13T13:29:34.186Z
> Category: Öneri Sistemleri
> Module: Module 3: Evaluation Protocols
**TLDR:** Full mathematical definition of 8 main accuracy metrics, from-scratch NumPy implementation, comparative run on MovieLens, and which metric to choose when — recommender engineer's metric cheat sheet.