Litres.
I would use either cubic centimeters or cubic inches.
no
cm
Grams.
Centimeters and grams.
Kilograms
There is really no such thing as a "liquid" unit. The unit of measure is for the VOLUME of something. The best unit for measuring the volume of a human bathtub would be the "Litre".
The density of a substance is the ratio of its mass to its volume. So, I would measure the mass and volume of a substance to calculate density.
My penis
you measure liquid or volume.
You would determine the volume of water it displaces and measure it.
You would use a tape measure.
volume