Instrument used for measuring the density or relative density of liquids is known as

The amount of matter per unit volume is known as density. Formula $\rho =\frac{M}{V}$The density of a substance in relation to another substance is known as its relative density. It has the form $\rho r=\frac{\rho }{w}$, $\rho w$ and $\rho g$ are the density of water and gas.
The tool used to determine relative density and density is called a hydrometer. William Nicholson created and refined the hydrometer in 1790. So, the density or relative density of liquids is measured using a hydrometer.