How much of earth's surface is used for food cultivation?

Question

How much of earth's surface is used for food cultivation?

Answer 1

Basically, if someone can use the ground to make money, they are.  So any ground that is potentially profitable and not in use for another purpose is being farmed.

Answer 2

All that is available -- even agriculturally marginal land -- except for individual homes which could grow veggies, herbs, etc. in their garden instead of flowers.

Answer 3

about 1% of earth surface not covered by water

Answer 4

The Earth's Diameter is 7926.41 miles.

  The surface area of Earth is 197.38 million square miles

  However, the Earth only has 57 million square miles of land (that's 36.48 billion acres; there are 640 acres per square mile). The rest is water

  Of this land area there are only 12 million square miles (7.68 billion acres) of arable land (used for food production). that comes out to be 6.1% of the earth's surface used for food production.