What is Magnitude in Physics (Definition)? What is magnitude in physics, we are going to talk about the quantities that have only magnitude and no directions. So for the magnitude definition, it is stated that the magnitude is the number of a quantity that shows how large or small the quantities are in comparison to their Reference Point. Magnitude is the maximum extent of size and direction of an object. Learn how to calculate magnitude for earthquakes, charges, forces and displacements with examples and FAQs. 5 meanings: 1. relative importance or significance 2. relative size or extent 3. mathematics a number assigned to a quantity,.... Click for more definitions. Discover the significance of magnitude in physics, exploring its types, applications, and real-world implications in measuring forces, energy, and natural phenomena.