Through a combination of direct satellite observations and modeling, they determined the total volume of ice tied up in the glaciers is nearly 41,000 cubic miles (170,000 cubic kilometers), plus or minus 5,000 cubic miles (21,000 cubic km).Oct 22, 2012

The World Ocean or global ocean is the interconnected system of Earth's oceanic waters, and comprises the bulk of the hydrosphere, covering almost 71% of Earth's surface, with a total volume of 1,332,000,000 cubic kilometres. Wikipedia
Area: 139.7 million mi²

41000mi3/139000000mi2=.0002949mix5280ft/mi=1.557ftx12in/ft=18.68in   Sorry, I was off by a factor of 10.  However, some of the glacier is submerged and water will take the place of the ice, and ice is about 1.1 times the volume of water.  Please correct me again if this calculation is wrong.