Submerge it in water and measure the amount of displaced water. That will be your displacement for the object, and will represent its volume.
Alternatively, if all faces of the object are flat, you could turn it into a geometry problem. If there are curved surfaces or surfaces resembling bubbles or bulges, and you know or can determine the equations that govern these surfaces, you can solve the problem with calculus.
The answer depends on what information you do have about the object.
Take an amount of water of which you know the volume. Drop the object in the water. Find the difference
Measure the object's mass using a scale. Measure the object's volume by calculating its dimensions (length x width x height). Divide the mass by the volume to find the density of the object. The unit of density will be mass per unit volume (e.g., g/cm3).
You can find the volume of an irregularly shaped object, like a rock, by using the water displacement method. Submerge the object in a known volume of water in a container. Measure the increase in water level, which equals the volume of the rock.
To calculate the density of an irregular shaped floating object, you can measure its mass using a balance and then find its volume by submerging it in a known volume of water and measuring the water displaced. For a regular shaped floating object, you can simply divide its mass by its volume to find the density.
Displacement method.... Is the method to find volume of an irregular object
To find the density of a regular shaped object, you can calculate it by dividing the mass of the object by its volume. For irregular shaped objects, you would measure the mass of the object using a scale, then measure its displaced water volume when submerged in a graduated cylinder. The density can then be calculated by dividing the mass by the volume of water displaced.
When you are trying to find the volume of an irregularly shaped object.
Measure the volume of the object which is same as the volume of the displaced liquid in which that sinks. And measure the mass of the same object from a weighing machine. then use density = mass/volume
Make a mold of the object and then fill the mold with water and measure the volume of the water.
lenght x weight x height
water displacement