This can be derived with the definitions of pressure and bodyweight density. Look at an area at the bottom of a vessel of liquid. Pressure might also be expressed with regards to normal atmospheric pressure; the unit atmosphere (atm) is equal to this pressure, and also the torr is defined https://orlandocommercialpressure86420.wikifordummies.com/8138630/5_easy_facts_about_commercial_pressure_washing_services_orlando_described