How to determine cubic measurements. I have length, width, and depth. Do I simply multipy the three numbers?

72 x 28 x 33 = how many cubic inches?

I have length, width, and depth. Do I simply multiply the three numbers?

72 x 28 x 33 = how many cubic inches?

Yes. That's how it's done.

For the units, 72\, inches \,\times\, 28\, inches \,\times\, 33\, inches = 66528\, inches^3\,( 66528\, cubic\,inches)

In case these were cm, the units would be cm^3, or if they were in metres, m^3 and so on.