A great way to calculate this is by simply knowing the diameter of the earth in kilometers, which is: 12,742 kilometers (km). After you know that, the surface area of a sphere is 4*pi*r^2 so 4*pi*(12742/2)^2.
An automatic calculator for determining the surface area from radius is as follows:
Surface area calculatorNote the units will be whatever units you are entering but squared. For example, if you enter kilometers, the surface area will be kilometers^2.
A side note that I find interesting is the earth can be considered to be a globe – although it is actually more of a slightly squashed globe because of how the earth cooled while spinning.