exactly how many gallons of water would it take to raise the worlds sea level 1 inch?

I will keep this simplified as possible, not taking continents into consideration and rounding off at each step

1) You need the radius of the earth.

Calculate the volume of the earth (sphere) 4/3 Pi r³

now add an inch the radius and calulate the difference in volume.

Earth is about 6371 km in radius

this comes to about 250,826,771.7 inches

Volume normal:

66,101,340,604,400,629,555,409,916 cu. in.

Volume with 1 inch more radius:

66,101,341,893,616,611,619,816,324 cu. in

Difference of 1,289,215,982,064,406,408 cu. in.

=21,126,464,807,912,279,930 cu. cm. (2.54*2.54*2.54) cu cm /in³

=21,126,464,807,912,280 litres (1000 cu cm = 1 litre)

=5,581,628,747,136,665,767 gallons (1 gal = 3.785 litres)

I don't know the exact numbers, but I would imagine you would need the current volume of the area to be covered, and then figure out the size of an area that a gallon of water would cover at 1 inch deep. Then it's just a matter of dividing the 2 numbers.

Here's something to wrap your brain around...

Imagine how much the earth's water level would lower if we were to remove all the aquatic life and man made objects from the oceans.

I think I would find the total volume of the ice on the planet, then divide it by 25.