OK the question looks silly but since you posted the question I'll give you a way to answer it...

Sand is defined as grains that measure from 1/400 inch (0.06 millimeter) to 1/12 inch (2.1 millimeters) in diameter. This corresponds to specific weight of 0.30 - 13 mg

How sure we are ?

Using the ranges of diameters, you can obtain the volume of the sand grain by using the formula for the volume of a sphere

volume = 4/3π·radius3

To find the diameter:

density = mass/volume

Therefore sand diameter = 0.060 mm diameter = 2.10 mm

Now the Math part where you would like to use the calculator.

Take the 0.060 mm as your sand reference:

1km is equivalent to 1,000,000 mm so therefore the lateral number of sand grain in 1km is about 16,666,666 and therefore one square kilometer of Sahara Desert will hold a lateral number of sands of about 6.125 x 10 to the 15th power. (that is you multiply 16,666,666 twice)

SAHARA Desert is about 9,000,000 square kilometer. Therefore:

(9M )x 6.125x10 15th power will give you the lateral number of sands (surface area number). That's a lot !!!

The challenging part - you consider now the volume. Meaning we are onely talking about the surface number of the sands, we have not yet taken the sands below !!!...You can do this by multiplying the surface area number by the depth say 1 meter or 2 meters or 3 meters and so on and so forth...

So I would say YES the sands in the SAHARA desert can be really counted using calculator (provided it is the scientific calculator !!!)

Any more question ? how about the volumetric water quantity of the the Pacific Ocean? Just tell me the specific gravity and we will do the Math together.