Density is defined as the mass per unit volume of a substance or mixture of substances. A mixture may be either homogeneous or heterogeneous. Density for an entire mixture cannot be calculated for a heterogeneous mixture, since the particles in the mixture are not uniformly distributed, and the mass changes throughout the volume. For a homogeneous mixture, finding the density requires taking two simple measurements unless you have a hydrometer that can measure the density directly.
Measure the volume of the homogeneous mixture. If it is a liquid, pour some into a graduated cylinder. Read and record the volume. If the mixture is solid, pour some water into a beaker or graduated cylinder, read the volume and then place the solid in the water. Make sure the solid mixture is completely covered. Read the new volume and subtract the original volume to determine the difference. This difference is the volume of the solid mixture.
Place the mixture on a mass scale and read its mass. If it is liquid mixture, be sure to subtract the mass of the container holding the liquid.
Divide the mass by the volume to determine the density.