The density of pure aluminum at room temperature is 2.70 g/cm3. Commercial aluminum foil is sold by its area (square feet or square meters). Remove a roll of aluminum foil from the cardboard tube and weigh it. You get the mass divided by the density to get the total volume. Divide its volume by the area of the foil you purchased to get its thickness. The larger the mass you weigh, the more accurate your thickness estimate will be.
Be careful to make sure all layers are smooth, flat, and compressed so you are only measuring aluminum and not air. But be sure not to compress them too much as this will squeeze the aluminum even thinner.
Divide all thicknesses by the number of layers to get the thickness of the foil.
This method is better than measuring the thickness of one layer of foil because you can average the measurement error across all layers measured simultaneously.
Shift and prepare some squares of aluminum foil. Understand and control the size and area of each square.
In the beaker, add a known volume of liquid (water, oil, etc.) and drop it into the square aluminum foil. (Make sure there are no air bubbles attached etc - just foil. Make sure the aluminum sinks.) Drop enough squares in to measure the increase in liquid volume. (Aluminum has a density of 2.7 g/cm^3, so it sinks.)
