How much does a price move? That sounds simple, but measuring it accurately is actually quite tricky. A quick glance gives a rough idea, but traders, risk managers, and quantitative analysts need numbers they can really rely on — numbers that show true market turmoil without being fooled by odd data patterns. In this chapter, we’ll explore ways to measure volatility, from basic end‑of‑day calculations to high‑frequency tick‑by‑tick records.