Water makes up about 75% of the surface of the earth. However, 97% of the water on earth is salt water and therefore not easily used.
This means only 3% of the total water on earth is in the form of freshwater.
Now, let's consider only the total freshwater on earth which is equal to 8.5 quintillion gallons. The scale now changes so that each pixel is equal to 5.1 quadrillion gallons of water.
However, not all the freshwater is usable. 65% of the freshwater on earth is in either glacier or permafrost form.
This leaves us with only 35% of the earth's freshwater available to be used by humans and animals; That is, 1.785 quadrillion gallons of water.
Ideally, every person in any continent should have access to an equal amount of water. It's an equal world afterall.
The reality however, is quite skewed. As can be seen here, the per capita water availability is varied both by continent and by average individual income. The per capita water usage is also skewed across both continents and income.
Considering the daily water use in different countries, we can see that 1 person in the USA uses the same amount of water per day as is used by 144 people in the country of Mozambique